Bmp-realcostmanual v1.0

BMP-REALCOST

Best Management Practices – Rational Estimation of Actual Likely Costs of Stormwater Treatment

A SPREADSHEET TOOL FOR EVALUATING BMP EFFECTIVENESS AND LIFE CYCLE COSTS

User’s Manual and Documentation

Version 1.0

August 2010

Prepared by:

Chris Olson Larry A. Roesner

Colorado State University Department of Civil and Environmental Engineering

Fort Collins, CO 80523

&

Ben Urbonas Urban Watersheds Research Institute

Denver, CO

&

Ken MacKenzie Urban Drainage Flood Control District

2480 West 26th Avenue Suite 156-B

Denver, Colorado 80211

BMP-REALCOST Model User’s Manual and Documentation

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Table of Contents 1. INTRODUCTION .................................................................................. 1

1.1. DISCLAIMER ........................................................................................................ 1 1.2. HISTORY AND REVISIONS .................................................................................... 2 1.3. BMP-REALCOST OVERVIEW ........................................................................... 3 1.4. APPROPRIATE USE .............................................................................................. 4 1.5. ASSUMPTIONS ..................................................................................................... 4

2. MODEL STRUCTURE ......................................................................... 6 3. GETTING STARTED ........................................................................... 7

3.1. ENTERING REQUIRED INPUTS .............................................................................. 7 3.1.1. Project-Specific Cost and Precipitation Parameters .................................. 8 3.1.2. Watershed Parameters .............................................................................. 10

3.2. BMP PARAMETERS ........................................................................................... 13 3.3. GENERATING AND INTERPRETING MODEL RESULTS ......................................... 15

3.3.1. “Report” Worksheet ................................................................................. 16 3.3.2. “NPVCosts” Worksheet ............................................................................ 21 3.3.3. “CapitalCosts” Worksheet ....................................................................... 22 3.3.4. “OMCosts” Worksheet ............................................................................. 22 3.3.5. “WatershedLoading” Worksheet .............................................................. 22 3.3.6. “DischargeLoading” Worksheet .............................................................. 22 3.3.7. “Runoff” Worksheet.................................................................................. 22

4. ADVANCED OPTIONS ...................................................................... 23 4.1. MODIFYING RUNOFF MITIGATION VALUES ....................................................... 23 4.2. MODIFYING WATER QUALITY VALUES ............................................................. 23

4.2.1. BMP Effluent Event Mean Concentrations: ............................................. 23 4.2.2. Land Use Event Mean Concentrations: .................................................... 25

4.3. MODIFYING LAND COST VALUES ..................................................................... 25 4.4. MODIFYING BMP COST VALUES ...................................................................... 26

4.4.1. Editing Capital Cost Parameters .............................................................. 27 4.4.2. Editing Maintenance Cost Parameters ..................................................... 29

4.5. IMPORTING INPUTS FROM ANOTHER WORKBOOK .............................................. 32 5. TECHNICAL DETAILS ..................................................................... 33

5.1. PRECIPITATION DATA ....................................................................................... 33 5.2. WATERSHED IMPERVIOUSNESS ......................................................................... 33

5.2.1. Land Use Total Imperviousness ................................................................ 34 5.2.2. Source Controls ........................................................................................ 35 5.2.3. Land Use Effective Imperviousness .......................................................... 36

5.3. RUNOFF COEFFICIENTS ..................................................................................... 38 5.4. BMP SIZE ......................................................................................................... 38

5.4.1. Storage BMPs ........................................................................................... 39 5.4.2. Conveyance BMPs .................................................................................... 41 5.4.3. Permeable Pavements (PP) ...................................................................... 43

5.5. NUMBER OF BMPS ............................................................................................ 43 5.6. CONSTRUCTION COSTS ..................................................................................... 44

5.6.1. Development of Construction Cost Equations .......................................... 44


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5.6.2. Construction Cost Equations Used in Model............................................ 50 5.7. LAND COSTS ..................................................................................................... 51

5.7.1. Cost of Land Based on Land Use .............................................................. 52 5.7.2. Land Required for BMPs (CLC) ............................................................... 53

5.8. CONTINGENCY, ENGINEERING AND ADMINISTRATION COSTS ........................... 54 5.9. CAPITAL COST CALCULATIONS ......................................................................... 54 5.10. MAINTENANCE COST CALCULATIONS ............................................................... 57 5.11. REHABILITATION/REPLACEMENT COST CALCULATIONS ................................... 58

5.11.1. Reoccurrence Interval of Rehabilitation/Replacement Costs ................... 58 5.11.2. Rehabilitation/Replacement Costs as a Percentage of Construction Costs ................................................................................................................... 58

5.12. ADMINISTRATIVE COST CALCULATIONS ........................................................... 60 5.13. COST ADJUSTMENTS FOR TIME ......................................................................... 61 5.14. COST ADJUSTMENTS FOR LOCATION ................................................................. 61 5.15. NET PRESENT COST CALCULATIONS ................................................................. 62

5.15.1. Inflation Rate ............................................................................................ 63 5.15.2. Planning Horizon ...................................................................................... 64 5.15.3. Rate of Return ........................................................................................... 64

5.16. BMP EFFECTIVENESS CALCULATIONS .............................................................. 64 5.16.1. Runoff Volume Reduction ......................................................................... 64 5.16.2. Pollutant Load Reduction ......................................................................... 67 5.16.3. Cost Effectiveness ..................................................................................... 68

6. REFERENCES ..................................................................................... 72


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List of Figures Figure 1: Summary of pollutant load reporting chart ....................................................... 17 Figure 2: Summary of annual runoff volume reduction chart .......................................... 19 Figure 3: Annual capital and rehabilitation cost summary chart ...................................... 21 Figure 4: Annual maintenance and administrative cost summary chart ........................... 21 Figure 5: Capital cost input table ...................................................................................... 27 Figure 6: Chart showing example cost curves generated using the capital cost input tables........................................................................................................................................... 28 Figure 7: Map showing 2-Year, 1-Hour rainfall depths for locations near Denver, CO (UDFCD 2004). ................................................................................................................ 34 Figure 8: Effective imperviousness adjustments for Level 1 and Level 2 MDCIA. ........ 37 Figure 9: Diagram showing overland and channelized flow lengths assuming v-shaped watershed .......................................................................................................................... 43 Figure 10: Cost equations developed for constructed wetland basins, extended detention ponds and retention ponds with WQCV. .......................................................................... 45 Figure 11: Cost equations developed for sand filter basins, porous landscape detention, vaults with capture volume and sand filter vaults designed for the WQCV. .................... 46 Figure 12: Cost equations developed for permeable pavements. ..................................... 47 Figure 13: Cost equations developed for proprietary devices. ......................................... 48 Figure 14: Cost equations developed for extended detention ponds and retention ponds with EURV........................................................................................................................ 49 Figure 15: Unit construction cost equation developed for constructed wetland channels.50


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List of Tables Table 1 : Explanation of worksheet tab colors .................................................................... 6 Table 2 : Explanation of cell and column colors ................................................................ 6 Table 3 : Precipitation data for selected locations in Front Range of Colorado ............... 10 Table 4 : Land use types available within the model ........................................................ 12 Table 5 : Default values of total imperviousness for each land use type .......................... 12 Table 6 : Available BMP types for Site Control and Regional Control ........................... 13 Table 7 : Range of impervious acres applicable for each BMP ........................................ 15 Table 8: Summary of Water Quality Results table ........................................................... 16 Table 9: Summary of Runoff results table ........................................................................ 18 Table 10: Summary of Net Present Value Cost table ....................................................... 19 Table 11: Default values for runoff capture efficiency, volume and peak runoff reduction........................................................................................................................................... 24 Table 12: Table of land use average event mean concentrations for the Denver, CO region ................................................................................................................................ 25 Table 13: Unit Land Costs Based on Land Use ................................................................ 26 Table 14: BMP cost worksheet names .............................................................................. 26 Table 15: Maintenance cost input tables ........................................................................... 30 Table 16 : Table of correction factors for calculating runoff coefficients ........................ 38 Table 17: BMP design classification ................................................................................ 39 Table 18: Volume-based BMP design factors .................................................................. 40 Table 19: Summary of construction cost equations used in the model ............................. 51 Table 20: Land cost estimates as function of land use...................................................... 52 Table 21: CLC values used for computing BMP land costs ............................................. 54 Table 22: Default values of capital cost parameters used in the model ............................ 56 Table 23: Annual maintenance cost equations .................................................................. 57 Table 24: Rehabilitation/replacement cost percentages and frequency estimates ............ 60 Table 25: Engineering News Record 20-City construction cost index (1986-2008) ........ 61 Table 26: Engineering News Record regional cost indices (May 2008) .......................... 62 Table 27: Land use average EMCs in stormwater runoff for Denver, CO ....................... 67 Table 28: BMP Effluent EMCs used in the model ........................................................... 70 Table 29: Summary of BMPs that provide peak flow attenuation .................................... 71


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List of Appendices

Appendix A: Methods, sources and assumptions used to develop values for BMP

effluent and land use event mean concentrations Appendix B: Methods, sources and assumptions used to develop BMP construction

costs Appendix C: Methods, sources and assumptions used to develop BMP maintenance cost

equations


1

1. INTRODUCTION This section includes important information related to the purpose, development and

appropriate use of the model.

1.1. Disclaimer ATTENTION TO PERSONS AND ORGANIZATIONS USING ANY URBAN

DRAINAGE AND FLOOD CONTROL DISTRICT SUPPLIED OR SUPPORTED

SOFTWARE, SPREADSHEET, DATABASE OR OTHER PRODUCT.

It is likely that some nonconformities, defects, and errors with the products or their

intended use will be discovered as they are used. We welcome user feedback in helping

to identify these potential problems so that improvements can be made to future releases

of Urban Drainage and Flood Control District supplied or supported software,

spreadsheet, database or other product. Any of the aforementioned may be shared with

others without restriction provided this disclaimer accompanies the product(s) and each

user agrees to the terms that follow.

BY THE INSTALLATION AND/OR USE OF ANY URBAN DRAINAGE AND

FLOOD CONTROL DISTRICT SUPPLIED OR SUPPORTED SOFTWARE,

SPREADSHEET, DATABASE OR OTHER PRODUCT, THE USER AGREES TO

THE FOLLOWING:

NO LIABILITY FOR CONSEQUENTIAL DAMAGES

To the maximum extent permitted by applicable law, in no event shall the Urban

Drainage and Flood Control District, its contractors, advisors, reviewers, or its member

governmental agencies, be liable for any incidental, special, punitive, exemplary, or

consequential damages whatsoever (including, without limitation, damages for loss of

business profits, business interruption, loss of business information or other pecuniary

loss) arising out of the use or inability to use these products, even if the Urban Drainage

and Flood Control District, its contractors, advisors, reviewers, or its member

governmental agencies have been advised of the possibility of such damages. In any

event, the total liability of the Urban Drainage and Flood Control District, its contractors,

advisors, reviewers, or its member governmental agencies, and your exclusive remedy,


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shall not exceed the amount of fees paid by you to the Urban Drainage and Flood Control

District for the product.

NO WARRANTY

The Urban Drainage and Flood Control District, its contractors, advisors, reviewers, and

its member governmental agencies do not warrant that any Urban Drainage and Flood

Control District supplied or supported software, spreadsheet, database or other product

will meet your requirements, or that the use of these products will be uninterrupted or

error free.

THESE PRODUCTS ARE PROVIDED “AS IS” AND THE URBAN DRAINAGE AND

FLOOD CONTROL DISTRICT, ITS CONTRACTORS, ADVISORS, REVIEWERS,

AND ITS MEMBER GOVERNMENTAL AGENCIES DISCLAIM ALL

WARRANTIES OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING

BUT NOT LIMITED TO, ANY WARRANTY OF MERCHANTABILITY, FITNESS

FOR A PARTICULAR PURPOSE, PERFORMANCE LEVELS, COURSE OF

DEALING OR USAGE IN TRADE.

1.2. History and Revisions

BMP Whole Life Cycle Cost Effectiveness Analysis Tool - Version 1.0 (released August

2009) - Prepared by Chris Olson (Colorado State University) with Ben Urbonas (Urban

Watersheds Research Institute), Dr. Larry Roesner (Colorado State University) and Ken

MacKenzie (Urban Drainage Flood Control District).

BMP-REALCOST – Version 1.0

This model supersedes the previously-unnamed version 1.0 released in August 2009.

Permeable pavements now applied as site control BMPs instead of source

controls.

Changed land cost computations to be a function of the BMP size using the land

consumption coefficient (CLC) which relates the area of land consumed to the size

of the BMP.

BMP capture efficiency can now be edited by user on “RunoffMitigation”

worksheet


3

Rehabilitation/replacement costs are now amortized based on the number of years

of benefits that follow each occurrence. Generally this results in lower net present

costs than computed in previous versions.

Some land costs were revised to better reflect Denver-area costs.

Column for maintenance activity “beta” values were added to maintenance cost

tables

Cost charts were revised to show annual costs and cumulative costs

New chart was added to display scenario runoff reduction effectiveness

1.3. BMP-REALCOST Overview BMP-REALCOST was developed to assist engineers, planners, developers, consultants

and decision makers in determining the life cycle costs and effectiveness of structural

stormwater runoff best management practices (BMP) as they are applied within an

urban/suburban setting. The intent of this model is to provide the practicing professional

and decision maker with facts and fiscal information on what effects their choices will

have on the economic and environmental resources of the owners and/or the municipality

within which systems of stormwater management BMPs are implemented. The decisions

made to select the types of BMPs within a municipality and its new

developments/redevelopments will have many long-term ramifications that include (1)

the effectiveness in the protection of the receiving waters, (2) long-term cost of operating

and maintaining the BMPs, and (3) the administrative costs that the municipality will

need to budget for over the years to make sure that the BMPs deployed within its

boundaries continue to function as originally designed.

This model is built into Microsoft Excel format and many of the operations are performed

using macros written in Visual Basic for Applications. The model operates by first

having the user input information describing the physical characteristics of a watershed

that affect runoff quality and quantity (e.g., contributing area, land use, imperviousness,

etc.). Second, the user enters information that describes what type(s) of BMP(s) will be

applied to the watershed/development and the area (number of impervious acres) from

which each BMP will receive runoff. Next the user decides whether to use default cost

and BMP effectiveness values, or input their own. The model then takes the user-entered


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(or default) information and estimates the size of each BMP, determines the number of

BMP(s) needed to treat the watershed, produces estimates of average annual runoff

quality and quantity for the entire watershed/development, and calculates life cycle costs

for the BMP(s) selected.

1.4. Appropriate Use The model was developed as a planning-level tool, where some output accuracy is

sacrificed in order to make the model easy-to-use and require minimal data inputs. As

such, the model uses several simplifying assumptions which are further described within

this report. The results should not be used as a substitute for, or as a comparative

resource for, final BMP designs, more intensive rainfall/runoff modeling techniques or

“engineer’s estimates”.

The model was developed using many of the recommendations and methods provided in

the Urban Drainage Flood Control District’s (UDFCD) Urban Storm Drainage Criteria

Manual (USDCM) (UDFCD 2004), therefore this model should only be applied to areas

where the USDCM design criteria are valid.

1.5. Assumptions The following are fundamental assumptions used in developing the model.

1. The user has adequate knowledge of stormwater management to apply BMPs

appropriately, considering the land use and relative size of BMP. For example,

the effectiveness results of applying a sediment/oil/grease separator (SOG) to a

residential area may indicate that loading of certain constituents (such as metals or

oils) will actually increase after the BMP is installed. This could occur because

SOGs are typically installed in areas where high influent metals and oil loads

exist and although the SOG may remove some of the metals, a relatively high

concentration may be measured in the effluent. If the effluent concentration is

greater than the influent concentration, an apparent increase would result. In

addition, specifying a BMP to treat an area much larger or smaller than is

typically specified could cause both the costs and effectiveness to be highly

inaccurate.


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2. BMPs with water quality capture volume (WQCV) are assumed to effectively

treat 85% of the annual runoff. BMPs designed to capture the excess urban runoff

volume (EURV) effectively treat 98% of the annual runoff.

3. Unless otherwise noted (with EURV naming convention), BMPs with storage

volume are sized to store the water quality capture volume (WQCV) only. They

do not include additional storage for larger storms.

4. Computations for peak runoff rates using the Rational Method are made using

several simplifying assumptions for waterway length and conveyance length. See

Section 5.4.2.

5. Values for effluent event mean concentrations were not available for all of the

BMPs included in the model, therefore some values were substituted and/or

assumed until better information is available.

6. Values for land use event mean concentrations were not available for all of the

constituents included in the model; therefore some values were substituted and/or

assumed until better information is available.

7. BMP effectiveness does not change over time. It is assumed that adequate

maintenance will be performed to keep BMP effectiveness relatively consistent

from year to year.

8. The default maintenance costs were developed assuming proactive maintenance

(i.e. keeping facilities properly maintained), as opposed to reactive maintenance

(i.e. only performing maintenance once something breaks and/or the BMP

effectiveness is compromised). Through a series of interviews with agencies

responsible for BMP maintenance, overall it was generally agreed upon that

proactive maintenance is less costly than reactive maintenance.

9. The default costs for proprietary systems are assumed to be an average cost

considering the wide variety of systems available.

10. The computed costs for permeable pavement do not account for potential cost

savings from the reduced need for additional stormwater infrastructure, nor do

they account for the “foregone” costs of installing and/or maintaining typical,

impervious pavement. Without accounting for these cost savings, permeable

pavement will always appear to be a more expensive option.


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2. MODEL STRUCTURE The model was developed using multiple worksheets within a single Excel workbook. A

brief description of each worksheet is included on the “Information” worksheet that is

automatically loaded each time the model is opened. The worksheet tabs are color-coded

according to their intended use, as described in Table 1.

Table 1 : Explanation of worksheet tab colors Worksheet Tab Color Worksheet Purpose

Blue These worksheets contain cells that require the user to input information

Purple These worksheets contain cells that have default parameter values already defined (i.e. cost curves, event mean concentrations, etc.), but can be edited by the user if necessary.

Green These worksheets are “Read-Only” worksheets. Editing these worksheets may adversely affect model processes.

The model requires many input parameter values, some of which must be defined by the

user and others that are computed automatically by the model. Each parameter is

categorized and color-coded (similar to worksheet tabs) as described in Table 2.

Table 2 : Explanation of cell and column colors Cell/Column Color Category Purpose

Blue User-Defined

The user must enter a value, make a selection from a drop-down box, or use the default value already entered (if available).

Green Model-Defined

These cells/columns are “read-only” and are populated automatically by the model. Editing these cells and/or columns may adversely affect model processes.

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Recall from Section 2 that cells or columns color-coded in blue require the user to input a

value or use the default value (if provided). Green cells or columns cannot be modified

by the user.

3.1.1. Project-Specific Cost and Precipitation Parameters The model requires several parameters for project-specific precipitation and life cycle

cost calculations. Some default values have been entered that generally should be

applicable to the Denver, Colorado region, however because some of these values are

likely to vary from project to project it is recommended that the user review and verify

the applicability of the default values before using them. Each required parameter is

described below.

Planning Horizon

The planning horizon of the project(s) defines the time over which the net present value

of the project costs will be estimated. The default value is 50 years and is the value

recommended by UDFCD and other water resource organizations, recognizing the

longevity of such projects and the difficulty in financing their construction.

Current ENR Construction Cost Index

The user should input the current Engineering News Record (ENR) Construction Cost

Index (CCI) for the region of analysis, to adjust the default costs used in the model for

50 Default

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Project-Specific Precipitation and Cost Parameters

Planning Horizon (yrs)

Rate of Return (%)

Admin. Costs as % of Maint. (%)

Select Location for Precip. Values

Inflation Rate (%)

Mean Annual Precipitation (in)

2-Year, 1-Hour Precipitation (in)

Current/Regional ENR CCI

0.43Mean Storm Depth (in)

Default

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9

time and location. Default costs were programmed into the model in May 2008 dollars,

based on the 20-City averaged ENR CCI (ENR CCI: 8141).

Inflation Rate

The inflation rate describes how costs will increase in the future. The default value is

4.6%, which is the historical annual increase of the ENR CCI from 1958 to May, 2008

(ENR 2008). UDFCD recommends using a 50-year planning horizon analysis for large

projects; however the user may choose to use a different inflation rate value (based on

more recent trends) if the planning horizon of the project is not 50 years.

Rate of Return

The rate of return describes how monies that are set aside now for future costs will

appreciate into the future. The default value used is 5%, however the rate may vary from

agency to agency and a reasonable estimate is probably available from the municipality’s

financial manager.

Administrative Costs

The additional costs for the administration of a BMP maintenance program are accounted

for by entering a value (percentage) that defines the administration costs as a percentage

of the annual maintenance costs. The default rate is 12%, however this rate may vary

from agency to agency and a reasonable estimate is may be available from the

department’s manager.

Precipitation

The user selects a location (from the drop-down box) that is closest to the location of the

project. This selection then specifies the precipitation data to be used by the model. The

user also has the option of selecting “Other” as the location of the project and entering

precipitation values specific to the project location. Two separate precipitation values are

used by the model. The first is the average annual precipitation depth, which is used in

calculating annual runoff volume and pollutant loadings generated from the watershed.

The second is the 2-Year, 1-Hour rainfall depth which is used for calculating the

appropriate size of BMPs that are designed to treat a specified flowrate. The

precipitation values for each available location are presented in Table 3.


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Table 3 : Precipitation data for selected locations in Front Range of Colorado Location Mean Annual Precipitation (in) 2-Year, 1-Hour (in) Arvada 15.8 0.95 Aurora 15.8 1.0 Boulder 15.8 0.87 Denver Metro 15.8 0.95 Lakewood 15.8 0.99 Longmont 15.8 1.02 Parker 15.8 0.97 Westminster 15.8 0.98 Sources: Mean Annual - National Weather Service (2008) 2-Year, 1-Hour – Figure RA-1 in USDCM, Vol. 1 (UDFCD 2004)

Mean Storm Depth

The user inputs the mean storm depth for the location of the project. (The default value

of 0.43 inches is applicable for the Front Range of Colorado). This value is used to

compute the size of volume-based BMPs. A map of mean storm depths across the

contiguous United States can be accessed by clicking on the “?” button.

3.1.2. Watershed Parameters This section describes how runoff-generating characteristics of a watershed of interest

should be input into the model.

Delineating Subcatchments

First, the user must identify the total number of subcatchments located within the area of

interest. The steps for doing so are described below. Note that the total number of

subcatchments cannot exceed 40 in one workbook.

As the spreadsheet layout suggests, each subcatchment can only have one value for

contributing area, land use, total imperviousness, source controls, effective

imperviousness, soil type, runoff coefficient, BMP type, and BMP density (i.e. number of

impervious acres contributing per BMP). The following protocol is recommended for

determining the number of subcatchments needed within a watershed:

1. Determine the number of land uses in the watershed. Assign a subcatchment to

each land use and calculate a contributing area.


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2. For each subcatchment, is there more than one type of source control being

implemented? If yes, then divide the subcatchment(s) up by source control.

3. For each subcatchment, is there more than one type of soil present? If yes, than

divide the subcatchment(s) up by soil type.

4. For each subcatchment, is there more than one type of BMP being applied? If

yes, then divide the subcatchment(s) up by BMP type.

5. For each subcatchment, will each individual BMP within that subcatchment

capture runoff from a (relatively) equal area? (In other words, if more than one

BMP is to be implemented within the same subcatchment, does each BMP have

an equal number of impervious acres draining to it?). If not, than divide the

subcatchment into additional subcatchments, so that the appropriate number of

impervious acres draining to each BMP can be input.

6. For each subcatchment, is the slope relatively uniform? If no, then divide the

subcatchment(s) into additional subcatchments and calculate the slope for each.

Also recalculate the contributing area of all subcatchments.

Entering Subcatchment Parameters

Once the total number of subcatchments (each with its own unique combination of

watershed parameters) is determined, then the watershed parameters may be entered as

described in the following steps. Input of the watershed parameters follows a left-to-right

progression from column to column for each subcatchment, starting with Column C.

For each subcatchment:

1. Enter a subcatchment ID in Column C (this is optional…the model will still run if

left blank).

2. Enter a contributing area in total acres in Column D.

3. Select a land use type from the dropdown list in Column E. The available land

use types are presented in Table 4.

Subcatchment No. Subcatchment ID Area (ac) Land Use

Total Imperviousn

ess (%)

Source Control

(LID)

Effective Imperviousn

ess (%) NRCS

Soil TypeSubarea

Slope (%)

Effective Runoff

Coefficient

1 50.00 Commercial 95% PP 95% C 1.00% 0.80

Watershed Parameters


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Table 4 : Land use types available within the model Land Use Type

Commercial Industrial – Light Industrial – Heavy

Residential – Single Family (1,000 sf) Residential – Single Family (2,000 sf) Residential – Single Family (3,000 sf) Residential – Single Family (4,000 sf) Residential – Single Family (5,000 sf) Residential – Multi-Unit (detached) Residential – Large Lot (>1/2 acre)

Residential – Apartments Parks, Cemeteries

Institutional (universities, office parks) Paved Areas Undeveloped

4. Enter a value for total imperviousness in Column F, OR, click on the “Enter

Default Imperviousness Values” button to have the model automatically fill in the

values based on UDFCD recommended values (shown in Table 5 below). When

all values are updated, the button will turn from red to green.

5. Select an appropriate source control method from the dropdown list in Column G

to apply to the subcatchment. (For more information on applying/selecting source

controls, see Section 5.2.2).

6. Enter a value for effective imperviousness in Column H, OR, click on the

“Calculate Effective Imperviousness” button to have the model automatically

compute the values based on UDFCD protocols. When all values are updated, the

button will turn from red to green. (For more information on how effective

imperviousness is computed, see Section 5.2.3).

Table 5 : Default values of total imperviousness for each land use type Land Use Type Percent Imperviousness Commercial 95 Industrial – Light 80 Industrial – Heavy 90 Residential – Single Family (1,000 sf) 28* Residential – Single Family (2,000 sf) 39* Residential – Single Family (3,000 sf) 51* Residential – Single Family (4,000 sf) 62* Residential – Single Family (5,000 sf) 72*


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Residential – Multi-Unit (detached) 60 Residential – Large Lot (>1/2 acre) 27* Residential – Apartments 80 Parks, Cemeteries 5 Institutional 50 Paved Area 100 Undeveloped 2 Source: UDFCD Design Manual, Vol.1 – Table RO-3

* - Average values taken from Figures RO 3-5 in UDFCD Design Manual, Vol. 1

7. Select the dominant NRCS soil type for the subcatchment from the dropdown list

in Column I.

8. Enter the average slope of the subcatchment as a percentage in Column J. The

slope should be relatively uniform throughout the subcatchment for best results.

9. Enter a value for effective runoff coefficient in Column K, OR, click on the

“Calculate Runoff Coefficients” button to compute the value based on UDFCD

protocols. When all values are updated, the button will turn red to green. (For

more information on how effective runoff coefficients are computed, see Section

5.3).

3.2. BMP Parameters The section describes how to apply BMPs to the subcatchments. The first step is to

determine whether to apply a single regional-control BMP or multiple site-control BMPs.

The regional control BMP will treat runoff from all of the subcatchments combined,

whereas site-control BMPs are applied at the subcatchment level only. The BMP types

available for each type of control are presented in Table 6.

Table 6 : Available BMP types for Site Control and Regional Control Site Control BMPs Regional Control BMPs Concrete Grid Pavers(1) Constructed Wetland Basin Constructed Wetland Basin Constructed Wetland Channel Constructed Wetland Channel Extended Detention Basin - WQCV(2) Extended Detention Basin- WQCV(2) Extended Detention Basin - EURV(3) Extended Detention Basin - EURV(3) (U) Inlet Inserts Retention Pond - WQCV(2) None Retention Pond - EURV(3) Porous Landscape Detention – Infiltration(4) Sand Filter Basin – Infiltration(4) Porous Landscape Detention – Underdrain(5) Sand Filter Basin - Underdrain(5) Retention Pond – WQCV(2)


14

Retention Pond – EURV(3) Sand Filter Basin – Infiltration(4) Sand Filter Basin - Underdrain(5) (U) Media Filter Vault Sand Filter Vault (U) Hydrodynamic Separator (U) Sediment/Oil/Grease Separator (U) Vault w/ Capture Volume Notes: (1) – Type of permeable pavement, designed for infiltration or underdrained (2) – BMPs designed to capture water quality capture volume only (3) – BMPs designed to capture the excess urban runoff volume (4) – BMPs designed to infiltrate full water quality capture volume (5) – BMPs designed with underdrains

Regional-Control BMPs

To apply a regional-control BMP, follow these steps.

1. Select the regional-control BMP button

2. Select the BMP to be applied from the dropdown list in Cell O24.

3. Input a land cost value into Cell T24 for the location where the regional BMP will

be installed. For applicable land costs for different land use types, reference the

table on the “LandCosts” worksheet.

4. Click on the “Calculate BMP Sizes” button to compute the size of the BMP

required. The button will turn green when all values are updated.

Site-Control BMPs

To apply a site-control BMP, follow these steps.

1. Select the site-control BMP button.

2. Select the BMP to be applied to each subcatchment in Column O.

Select Regional-Control BMP

Select Site-Control BMP


15

3. For all BMPs that are NOT permeable pavements, enter the number of impervious

acres that will runoff to each individual BMP located within the subcatchment

into Column P. The value entered should be within the ranges presented in Table

7 for best results. If the number of impervious acres draining to each BMP is less

than the total number of impervious acres in the subcatchment, then more than

one BMP will be applied, each with the same number of impervious acres

contributing. Inappropriately applying very large or very small impervious areas

to certain BMPs may result in unrealistic results. For these types of BMPs, no

value is needed in Column Q.

4. For permeable pavement BMPs, enter the number of impervious acres that will

“run-on” to the permeable pavement (RAPP), not including the permeable

pavement into Column P. Then, enter the surface area of the permeable pavement

(SAPP) into Column Q. The ratio of RAPP:SAPP should be less than or equal to

5 to ensure that PPs do not clog too fast. In other words, no more than 5

impervious acres may “run-on” to 1 acre of permeable pavement.

5. Click on the “Calculate BMP Sizes” button to compute the size and number of the

BMPs required for each subcatchment. The button will turn green when all

values are updated.

3.3. Generating and Interpreting Model Results To generate model outputs, select the “Report” worksheet and click on the “Update

Summary Report” button to generate/update summary results.

Model results are output into several different worksheets, each of which is described in

the following sections.

Table 7 : Range of impervious acres applicable for each BMP

BMPs Impervious Acres to each BMP

Minimum Maximum Constructed Wetland Basin 2 - Constructed Wetland Channel 2 - Extended Detention Basin - WQCV(1) 2 - Extended Detention Basin - EURV(2) 2 - (U) Inlet Inserts 0.1 0.25 Porous Landscape Detention – Infiltration(3) 0.1 5 Porous Landscape Detention – Underdrain(4) 0.1 5

Update Summary Report


16

Retention Pond – WQCV(1) 2 - Retention Pond – EURV(2) 2 - Sand Filter Basin – Infiltration(3) 0.1 5 Sand Filter Basin - Underdrain(4) 0.1 5 Media Filter Vault 0.1 2 Sand Filter Vault 0.1 2 (U) Hydrodynamic Separator 0.1 2 (U) Sediment/Oil/Grease Separator 0.1 2 (U) Vault w/ Capture Volume 0.1 2 Permeable Pavements (1)

Notes: (1) - Permeable pavements can have unlimited size as long as the impervious run-on area is equal to or less than 5x the PP surface area

3.3.1. “Report” Worksheet The “Report” tab of the spreadsheet summarizes the costs and effectiveness of the

selected BMP scenario in tabular and chart forms.

Summary of Water Quality Table

The water quality results summary table is presented as Table 8.

Table 8: Summary of Water Quality Results table

The values displayed under the heading “Watershed Pollutant Load” are the sum of

annual pollutant loads generated from all subcatchments. It is presumed that these would

be the pollutant loadings to the receiving water if no source controls or BMPs were in

place.

Dissolved Copper1.100.49

79%$72,027.71

$269,362.71$115,173.35

82%$52,834.4970%

38%

2.41

36.1358.65

0.7373%

Total Kjeldahl Nitrogen

$15,783.30$1,768.58

10.71

$19,981.32$3,947.49

1.67

84.15 60%53%

Constituent

Discharged Pollutant Load

(lb/yr)

Pollutant Reduction

Total Suspended Solids $19.01($/lb)

Cost per Unit Removed

5737.69 82%

Watershed Pollutant Load

(lb/yr)1060.49

(%)

Total Nitrogen

6.12Dissolved Zinc

Total Zinc

0.32

0.27Total Lead 1.50

5.0833.89

0.42

0.23

0.09

Total Phosphorus

70%$342,792.22

Dissolved LeadTotal Copper

53%


17

The values displayed under the heading “Discharged Pollutant Load” are the total

annual pollutant loads entering the receiving water from all subcatchments, with the

selected source controls and BMP(s) in place. These values account for pollutant

reductions due to infiltration and treatment of runoff within the source controls and

BMPs.

The values displayed under the heading “Pollutant Reduction” are the annual percent

reduction of each pollutant that is achieved with the selected source controls and BMP(s)

in place.

The values displayed under the heading “Cost per Unit Removed” are the total life

cycle costs for removing one unit of pollutant during the planning horizon of the project.

The “Summary of Watershed and Discharged Pollutant Loads” chart (Figure 1)

graphically presents the values in the summary table.

Figure 1: Summary of pollutant load reporting chart

Summary of Runoff Table

The Runoff summary table is presented as Table 9.

0

1

10

100

1,000

10,000

TotalSuspended

Solids

TotalPhosphorus

TotalNitrogen

TotalKjeldahlNitrogen

Total Zinc DissolvedZinc

Total Lead DissolvedLead

Total Copper DissolvedCopper

An

nu

al L

oa

din

g t

o W

ate

rbo

dy

(lb

)

Watershed Pollutant Loading Discharged Pollutant Loading


18

Table 9: Summary of Runoff results table

The values displayed under the heading “Watershed Runoff” are the total annual runoff

volumes (in cubic feet) generated from each subcatchment, if no source controls or

BMP(s) were in place. These volumes are a function of the precipitation and runoff

coefficient computed using the total imperviousness. If a regional BMP is being used

than only one row of values will appear representing the total runoff volume from all

subcatchments together.

The values displayed under the heading “Discharge to Receiving Water” are the total

annual runoff volumes entering the receiving water from each subcatchment, with the

selected source controls and BMPs in place. These values account for runoff reduction

due to losses such as infiltration and evaporation that occur within the selected source

controls and BMP(s). If a regional BMP is being used than only one row of values will

appear representing the total discharge volume from the regional BMP.

The values under the heading “Runoff Reduction” are the annual percent reduction of

runoff volume from each subcatchment that is achieved with the selected source controls

and BMP(s) in place.

The values under the heading “Peak Flow Control” inform the user which

subcatchments utilize BMPs that can be designed to control peak flows discharged to

receiving waters.

Subcatchment No. (ft3/yr)

2,068,777

Discharge to Receiving Water

27%446,515

27%

128%

Watershed Runoff

Runoff Reduction

Peak Flow Control

(ft3/yr) (%)

5 2,115,370

1,506,131

2,243,772Yes

5%3,996,626

2,009,601

Yes27%2,917,537

2 620,6333 3,073,6614

Yes

Summary of Average Annual Runoff Results

YesYes

Totals 590,2281,273,079 667,761 48%


19

The “Summary of Annual Runoff Volume Reduction” chart (Figure 2) graphically

presents the total runoff generated from the subcatchments, the runoff reduced due to

source controls and BMPs and the total runoff discharged to the receiving waters.

Figure 2: Summary of annual runoff volume reduction chart

Summary of Costs

The Cost summary table with example data is presented as Table 10.

Table 10: Summary of Net Present Value Cost table

2,671,045

589,851

1,831,418

Total Runoff Discharged (CF)

Runoff Reduced due to Source Controls (CF)

Runoff Reduced due to BMPs (CF)

$626,711$55,646

NPV of Capital Costs

$34,254$69,673

$196,822$4,636

$567,318$272,158

Summary of NPV Costs

$106,445$198,488

NPV of Maintenance

Costs

NPV of Rehabilitation

Costs

NPV of Administrative

Costs

$147,767$275,543

$26,809$19,865

$531,843$25,335

All Costs for 50 years

$135,373$975,017 $1,061,634Total NPV $3,159,314

$987,291


20

The values displayed in each cell are the net present value of the costs associated with the

selected source controls and BMPs for each subcatchment. If a regional BMP is being

modeled, than only one row of values will appear representing the total costs for the

regional BMP and any source controls applied. All costs are summed and reported as the

“Total NPV” value.

The “Annual Cost Summary” charts (Figure 3 and Figure 4) graphically displays the

annual and cumulative costs for capital, rehabilitation, maintenance, and administration

of all BMPs for the defined planning horizon.


21

Figure 3: Annual capital and rehabilitation cost summary chart

Figure 4: Annual maintenance and administrative cost summary chart

3.3.2. “NPVCosts” Worksheet

Capital/Rehabilitation Costs

$0

$2,000,000

$4,000,000

$6,000,000

$8,000,000

$10,000,000

$12,000,000

0 5 10 15 20 25 30 35 40 45 50

Year

An

nu

al C

ost

s

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

Cu

mu

lati

ve

Co

sts

Cumulative Costs Annual Costs

Maintenance and Administrative Costs

$0

$20,000

$40,000

$60,000

$80,000

$100,000

$120,000

$140,000

$160,000

$180,000

$200,000

0 5 10 15 20 25 30 35 40 45 50

Year

An

nu

al C

os

ts

$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

$3,000,000

$3,500,000

$4,000,000

Cu

mu

lati

ve

Co

sts

Cumulative Maintenance Cumulative Admin Annual Maintenance Annual Admin


22

The “NPVCosts” worksheet presents a breakdown of all annual costs over the defined

planning horizon of the project. This worksheet is “Read-Only” and any modifications to

it may adversely affect model computations. The equations used to calculate each value

are described in Section 5.15.

3.3.3. “CapitalCosts” Worksheet The “CapitalCosts” worksheet summarizes the capital and rehabilitation costs of the

BMPs selected for each subcatchment. This worksheet is “Read-Only” and any

modifications to it may adversely affect model computations.

3.3.4. “OMCosts” Worksheet The “OMCosts” worksheet summarizes the maintenance and administrative costs of the

BMPs selected for each subcatchment. This worksheet is “Read-Only” and any


3.3.5. “WatershedLoading” Worksheet The “WatershedLoading” worksheet summarizes the annual pollutant loads generated

from each subcatchment. These loads are what would enter the receiving water(s) if no

source controls or BMPs were implemented. This worksheet is “Read-Only” and any


3.3.6. “DischargeLoading” Worksheet The “DischargeLoading” worksheet summarizes the annual pollutant loads for each

subcatchment that would enter the receiving water(s) using the selected source controls

and BMP(s). This worksheet is “Read-Only” and any modifications to it may adversely

affect model computations.

3.3.7. “Runoff” Worksheet The “Runoff” worksheet summarizes the annual runoff volumes that are generated from

the contributing area, reduced through various source control and BMP processes

(evaporation, infiltration, etc.), and released to the receiving water(s) for each

subcatchment. It also shows which subcatchments have BMPs in place that will attenuate

peak flows. This worksheet is “Read-Only” and any modifications to it may adversely

affect model computations.


23

4. ADVANCED OPTIONS This section describes how to modify or override the model’s default values in order to

more accurately represent a specific project. The default values included in the model are

based on best available information at the time of model release, and therefore should

only be modified or replaced with values are also based on sound science.

4.1. Modifying Runoff Mitigation Values The “RunoffMitigation” worksheet contains information used to evaluate the

effectiveness of BMPs at mitigating increased runoff volumes generated from

urbanization. Each BMP has three values associated with it. The first value under the

“Runoff Capture Efficiency” heading is the percentage of annual runoff that is captured

and fully treated by the BMP. The second value under the “BMP Runoff Volume

Reduction” heading is the percentage of total runoff volume that is “lost” (i.e. not

discharged through the BMP outlet) within the BMP, generally due to infiltration and

evapotranspiration processes. The third value indicates whether or not the BMP is

capable of reducing peak runoff flows through losses and/or storage. The default values

for each parameter are presented in Table 11. Sources and methods used to develop

default parameter values are documented in Section 5.16.1.

4.2. Modifying Water Quality Values The “WaterQuality” worksheet contains information used in computing pollutant loads

with and without BMPs. The worksheet includes two tables of information, one

containing “BMP Effluent Event Mean Concentrations” and another containing “Land

Use Event Mean Concentrations”.

4.2.1. BMP Effluent Event Mean Concentrations: Values in this table are the concentrations of pollutants expected in the effluent

(discharge) of each BMP. The primary source of data for these values was the Analysis

of Treatment Performance Report (Geosyntec Consultants & Wright Water Engineers

2008), which documents expected BMP effluent EMCs based on statistical analyses of

the data in the International BMP Database (Geosyntec Consultants & Wright Water

Engineers 2009). However the report did not provide statistics for all BMPs included in

the model, therefore some additional analyses and assumptions were necessary. Details


24

of how these values were developed are included in Appendix A. The user may edit these

values if needed, however it is not recommended unless they are being replaced by values

reported in an updated version of the report cited above. Any updated versions of the

analyses report should be available at www.bmpdatabase.org

Table 11: Default values for runoff capture efficiency, volume and peak runoff reduction

BMP Runoff Capture

Efficiency (%)

Runoff Volume

Reduction (%)

Peak Runoff

Reduction Capability

Concrete Grid Pavers - Infiltration (1) 100% Yes Concrete Grid Pavers - Underdrain (1) (2) Yes Constructed Wetland Basin 85% 5% Yes Constructed Wetland Channel 85% 0% Yes Extended Detention Basin - WQCV 85% 30% Yes Extended Detention Basin - EURV 98% 30% Yes Hydrodynamic Separator 85% 0% No Inlet Inserts 85% 0% No Media Filter Vault 85% 0% No Porous Concrete Pavement - Infiltration (1) 100% Yes Porous Concrete Pavement - Underdrain (1) (2) Yes Porous Gravel Pavement - Infiltration (1) 100% Yes Porous Gravel Pavement - Underdrain (1) (2) Yes Permeable Interlocking Concrete Pavers - Infiltration

(1) 100% Yes

Permeable Interlocking Concrete Pavers - Underdrain

(1) (2) Yes

Porous Landscape Detention - Infiltration 85% 100% Yes Porous Landscape Detention - Underdrain 85% 53% Yes Reinforced Grass Pavement - Infiltration (1) 100% Yes Reinforced Grass Pavement - Underdrain (1) (2) Yes Retention (Wet) Pond - WQCV 85% 7% Yes Retention (Wet) Pond – EURV 98% 7% Yes Sand Filter Basin - Infiltration 85% 100% Yes Sand Filter Basin – Underdrain 85% 30% Yes Sand Filter Vault 85% 0% No Sediment/Oil/Grease Separator 捔脈㔀 0% No Vault w/ Capture Volume 85% 0% Yes Notes: (1) - λ = min(100% - (RAPP/SAPP)*5%, 95%) (2) - θ = max(50% - (RAPP/SAPP)*3%, 10%)

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26

implementation. These costs are considered applicable for new developments on

previously undeveloped land or land on which any existing structures have minimal

value. The costs associated with redevelopment, are likely to be higher due to the value

of structures already existing on that land. The user may edit the values in the table with

values more representative of the project location if necessary

Table 13: Unit Land Costs Based on Land Use Land Use Unit Land Cost

($/acre) Commercial $200,000

Industrial – Light $200,000 Industrial – Heavy $200,000

Residential – Single Family $130,000 Residential – Multi-Unit (detached) $175,000 Residential – Large Lot (>1/2 acre) $130,000

Residential – Apartments $200,000 Parks, Cemeteries $35,000

Institutional $130,000 Paved Area $200,000

Undeveloped $35,000

4.4. Modifying BMP Cost Values The default cost parameters for each BMP are located on separate worksheets, each

named with an abbreviation of the BMP (Table 14).

Table 14: BMP cost worksheet names Worksheet Name BMP CGP Concrete Grid Pavers CWB Constructed Wetland Basin CWC Constructed Wetland Channel EDB (WQCV) Extended Detention Basin w/ WQCV only EDB (EURV) Extended Detention Basin w/ EURV HS Hydrodynamic Separator II Inlet Inserts MFV Media Filter Vault PCP Porous Concrete Pavement PGP Porous Gravel Pavement PICP Permeable Interlocking Concrete Pavers PLD Porous Landscape Detention RGP Reinforced Grass Pavement RP (WQCV) Retention (Wet) Pond w/ WQCV only RP (EURV) Retention (Wet) Pond w/ EURV


27

SFB Sand Filter Basin SFV Sand Filter Vault SOG Sediment/Oil/Grease Separator VCV Vault w/ Capture Volume

For all of the cost worksheets, the user can input a value into any blue-shaded cell and

that input value will override any default value included in the model. Other options are

described below.

4.4.1. Editing Capital Cost Parameters

The capital cost input table is presented in Figure 5. First, select the option to use by

clicking on the appropriate selection button shown below. To compute capital costs, the

user has the option of using a parametric equation (Option 1) or using a cost-curve

generating option (Option 2). Option 1 is the default option.

Figure 5: Capital cost input table

Default UserBase Cost (C) = $23,897.00Unit Cost (X) = $0.89

Economy of Scale (α) = 1Cont/Eng/Admin (CEA) = 40.00%

CLC = 2.30E-05Units (U) =

Unit Cost per ft3 of storage (small) < ft3

Unit Cost per ft3 of storage (large) > 0 ft3

Other Base CostsCont/Eng/Admin (%)Other Costs (as % of base cost)

Notes:* Total land consumed uses the LCFCTR variable from Option 1

0.000023

Cost($) = (1+CEA)*(C+X*Uα)+(LC*IA*LCFCTR)

based on volume of storage (ft3)

Input

$0.70

1

$18,854.00

volume of storage (ft3)

Option 2

Option 1

40.00%

SelectedCapital Costs - Option 1 (default)

Capital Costs - Option 2

Option Buttons

Values used to calculate costs with Option 1

Blue cells are editable by user

“Small”project base cost

“Large”project base cost

Cost curve “knee” value


28

Option 1 Editing

If Option 1 is selected, the user may override any of the default values by entering a value

in the blue-shaded cell to the right of the default value cell. After doing so, the “Input”

value will change from the default value to the user-defined value. The “Input” value is

the value used in the model computations.

Option 2 Editing

If Option 2 is selected, the user must enter a value into each of the blue-shaded cells.

This option generates two linear cost functions which intersect at the value input into cell

“F27”, otherwise known as the “knee” in the curve. These two functions together

generate a cost curve, with higher unit costs for a BMP smaller than the “knee” value and

lower unit costs for a BMP larger than the “knee” value.

With both options, the user can view the cost curve (Figure 6) that is generated in the

chart located below the capital cost data entry cells. This allows the user to efficiently

determine the construction costs of a variety of BMP sizes.

Figure 6: Chart showing example cost curves generated using the capital cost input tables

EDB Capital Costs

$0

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

$800,000

$900,000

$1,000,000

0.1

0.8

1.7

2.6

3.5

4.4

5.3

6.2

7.1 8 8.

99.

810

.7

EDB Size (AF storage volume)

Co

st

Option 1

Option 2


29

4.4.2. Editing Maintenance Cost Parameters

The procedures for editing maintenance cost parameters on the maintenance cost table

(Table 15) are explained below.


30

Table 15: Maintenance cost input tables

Activity Units Default User Input Default User Input Default User Input Default User Input Default User Input Default User Input Default User Input

Compliance Inspection1each 1 1 0.33 0.33 1 1 $23.31 $18.39 100% 100% $10.15 $8.01 $0.00 $0.00 $14.78 - $14.78

Inlet/Outlet Cleaning each 6 6 0.5 0.5 2 2 $23.31 $18.39 100% 100% $10.15 $8.01 $0.00 $0.00 $40.79 - $244.71Nuisance Control each 12 12 0.5 0.5 1 1 $23.31 $18.39 100% 100% $10.15 $8.01 $35.00 $27.61 $50.01 - $600.11Outlet Maintenance each 0.25 0.25 12 12 3 3 $23.31 $18.39 100% 100% $102.88 $81.17 $200.00 $157.79 $2,455.97 - $613.99

0 0 0 $0.00 0% $0.00 $0.00 $0.00 - $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 - $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 - $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 - $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 - $0.00

The activities listed below are a function of the BMP size Annual Cost per AFLawn Mowing/Lawn Care acre 6 6 2 2 2 2 $23.31 $18.39 100% 100% $41.42 $32.68 $0.00 $0.00 $212.49 1 $1,274.91Sediment Removal (non-routine) CY 0.05 0.05 0.08 0.08 4 4 $23.31 $18.39 100% 100% $220.19 $173.72 $10.00 $7.89 $33.56 323 $541.96Sediment Removal (routine) CY 0.5 0.5 0.33 0.33 2 2 $23.31 $18.39 100% 100% $56.73 $44.76 $10.00 $7.89 $46.94 16 $375.49

0 0 0 $0.00 0% $0.00 $0.00 $0.00 $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 $0.000 0 0 $0.00 0% $0.00 $0.00 $0.00 $0.00

(1) - Compliance Inspection is added as an administrative cost Subtotal 1 $1,458.81Subtotal 2 $2,192.36

Beta ValueTotal Cost

per Unit Annual CostLump Sum

Per UnitOther Costs per UnitFrequency per Year Equipment Cost per HrHourly Labor RateHours per Unit Labor Crew Size

Annual maintenance costs as percentage of capital costsOR

Overhead Factor (%)

ANNUAL MAINTENANCE COSTS

“Constant” cost activities “Variable” cost activities

“Percentage” cost option


31

Selecting Cost Estimating Option

The user has two options for estimating annual maintenance costs. Option 1 (the default

option) is to develop bottom-up cost estimates using the information contained within the

maintenance activity cost table. Option 2 is to compute annual maintenance costs as a

simple percentage of the construction costs. To use and/or edit Option 1, continue with

the following directions.

Selecting Option 1 – Using Maintenance Cost Table

To estimate costs using the maintenance table, make sure that cell “M37” is blank. The

computational macros for this option only run when “M37” is blank.

Override Default Values in the Maintenance Cost Table

To override a default value from an existing activity in the maintenance cost table, input a

value into the blue-shaded “user” cell to the right of the “default” cell. The “input” cell

value will change from the default value to the user-defined value. The “input” value is

the value used by the model.

Deleting an Activity from the Maintenance Cost Table

To remove a maintenance activity from the maintenance table, simply delete all values in

the row of that activity. You will not be able to delete the equations in the green-shaded

cells as those cells are protected. To ensure that all data from deleted correctly, the value

in Column AG of that row should equal $0.00.

Adding an Activity to the Maintenance Cost Table

The maintenance table contains entry cells for two types of activities. The first activity is

one in which the annual costs will not vary significantly according to the size of the

BMP. These activities must be added in rows 18-26. The second activity type is one in

which the annual costs do vary significantly with the size of the BMP. These activities

must be added in rows 28-34.

To add an activity to the maintenance table, simply fill in appropriate values for each cost

component as is done with the default activities. The user should enter the values into the


32

blue-shaded “user” cells (not the white “default” cells) to signify that the activity has

been added by the user and is not a model default activity.

An example of how to determine the β-value is shown below. The derivation of β values

for default activities is described in Appendix C.

Example 1: An extended detention basin size (storage) is measured in AF and sediment

removal costs are estimated in cubic yards (CY). Sediment removal occurs once 20% of

the EDB storage is filled with sediment. We must find a β-value that relates the required

volume of sediment removal (in CY) to the size of the EDB (in AF).

Size)1AF(BMP

tRemoval)CY(Sedimen

AF

CY

)AF(BMPSize

tRemovalAF(Sedimenβ 323

1

1613

1

)2.0

By unit conversion, we find a β-value of 323.

Option 2 – Using Percentage of Construction Costs

To compute annual maintenance costs as a percentage of the BMP construction costs,

simple input the appropriate percentage value into cell “M37”. This will override the

values in the maintenance cost table (but the values will still be visible).

4.5. Importing Inputs from another Workbook Users can easily transfer their inputs and user-defined values to new versions of the

model using the “Import Data from Another Model” button found on the

“InputParameters” page. All user-defined information will be imported from the older

model to the new model, however the model must be re-run in order to generate results

with the newly imported data.


33

5. TECHNICAL DETAILS This section documents the methods used to compute BMP effectiveness and life cycle

costs.

5.1. Precipitation Data The model requires two precipitation parameter inputs, mean annual precipitation depth

and the 2-Year, 1-Hour total rainfall depth. The mean annual precipitation for the

Denver, Colorado region is 15.8 inches, as reported on the National Weather Service

website (NWS 2008). The 2-Year, 1-Hour rainfall depths for locations near Denver,

Colorado region are shown in Figure 7. A summary of precipitation data is provided in

Table 3.

5.2. Watershed Imperviousness Watershed imperviousness is a commonly used metric for describing the extent of

development in an urban area and empirical equations used to estimate BMP size and

rainfall-runoff relationships were developed as a function of the effective

imperviousness. The model uses “total” and “effective” imperviousness values in its

computations. Effective imperviousness is computed as a function of the total

imperviousness and the level of source controls applied to the watershed. Each is

described in the following sections.

B

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34

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35

5.2.2. Source Controls Source controls, also sometimes referred to as low impact development (LID) techniques,

refer to the use of grass buffers, grass swales, porous pavements and other features to

minimize directly-connected impervious areas (MDCIA), thus reducing effective

imperviousness. The model allows the user to choose from one of three levels of source

control; “Level 0”, “Level 1”, “Level 2”. Each option is described below. The affects of

implementing source controls on effective imperviousness are described in the following

section.

Level 0 – Level 0 source control generally refers to traditional development with roof

downspouts and driveways draining directly to curb and gutter systems.

Level 1 – The primary intent of Level 1 MDCIA is to direct the runoff from impervious

surfaces to flow over grass-covered areas and porous pavement, and to increase overland

travel time so as to encourage the removal of the heavier suspended solids before runoff

leaves the site, enters a curb and gutter, or enters another stormwater collection system.

Thus, at Level 1, as many of the impervious surfaces as possible are made to drain over

grass buffer strips before reaching a stormwater conveyance system (UDFCD 2004).

Level 1 source controls are less effective in areas with high total imperviousness because

there is not adequate space available to implement grass swales and buffer strips.

Level 2 - As an adjunct to Level 1, this level replaces solid street curb and gutter systems

with no curb or slotted curbing and low-velocity grass-lined swales and pervious street

shoulders. Conveyance systems and storm sewer inlets will still be needed to collect

runoff at downstream intersections and crossings where stormwater flow rates exceed the

capacity of the swales. Small culverts will be needed at street crossings and at individual

driveways until inlets are provided to convey the flow to a storm sewer (UDFCD 2004).

Level 2 source controls are less effective in areas with high total imperviousness because

there is not adequate space available to implement grass swales and buffer strips.


36

5.2.3. Land Use Effective Imperviousness Effective imperviousness is the percentage of a watershed that is impervious and drains

runoff directly to the paved or piped stormwater collection system. It is a function of the

total imperviousness and any source controls applied to the watershed, and is used to

compute the size of storage BMPs and the runoff coefficient used to estimate runoff

volume and peak flow rates. Empirical methods for estimating effective imperviousness

have been developed by UDFCD and are described below according to the level of

source controls applied.

None – When no source controls are implemented, the effective imperviousness is equal

to the total imperviousness.

Level 1 & Level 2 – Level 1 and Level 2 source controls reduce the effective

imperviousness by an amount that is dependent on the total imperviousness of the

watershed. The model uses UDFCD’s methods for reducing effective imperviousness, as

illustrated in Figure 8.

B

F

eq

LLL

W

MP-REALCO

Figure 8: E

or program

quations (1)

Level 0 Level 1 Level 2

Where EI = E

OST Model

Effective im

ming purpo

, (2) and (3)

Effective imp

mperviousne

oses, the plo

, which are i

EI EI 50.0

perviousness

37

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38

5.3. Runoff Coefficients UDFCD has developed empirical equations for estimating watershed runoff coefficients

as a function of the imperviousness of the watershed. The UDFCD equations are used in

the model and are provided below (UDFCD 2004).

12.0135.144.131.1 23 IIIKC AA for CA>0 otherwise CA=0 (4)

04.0774.0786.0858.0 23 IIIKC CDCD (5)

2/CDAB CCC (6)

Where I = watershed imperviousness (use total to compute total runoff generated, use

effective to compute total runoff that leaves a subcatchment), CA = runoff coefficient for

NRCS Type A soils, CB = runoff coefficient for NRCS Type B soils, CCD = runoff

coefficient for NRCS Type C & D soils, KA = correction factor for Type A soils (Table

16) and KCD = correction factor for Type C & D soils (Table 16).

Table 16 : Table of correction factors for calculating runoff coefficients

Soil Type Storm Return Period

2–Year 5-Year A 0 -0.08I + 0.09

C & D 0 -0.10I + 0.11

The model uses a 2-year return storm period (correction factors = 0) for generating runoff

and the 5-year correction factors are used to calculate the time of concentration for the

Rational Method.

5.4. BMP Size BMPs are classified as either storage BMPs, conveyance BMPs or PP (

Table 17). Storage BMPs capture and treat a specified volume of runoff and are

measured according to their design storage volume. Conveyance BMPs convey and treat

a specified flow rate and are measured according to their 2-year design flow capacity and

PPs are measured according to their surface area. The size of storage and conveyance

BMPs are computed as described in the following sections. PP surface area (SAPP) is

input by the user, therefore there is no “PP sizing” algorithm.


39

Table 17: BMP design classification

BMP Design Classification Concrete Grid Pavers PP

Constructed Wetland Basin Storage Constructed Wetland Channel Conveyance

Extended Detention Basin Storage Hydrodynamic Separator Conveyance

Inlet Inserts Conveyance Media Filter Vault Conveyance

Permeable Interlocking Concrete Pavers PP Porous Concrete Pavement PP Porous Gravel Pavement PP

Porous Landscape Detention Storage Reinforced Grass Pavement PP

Retention (Wet) Pond Storage Sand Filter Basin Storage Sand Filter Vault Storage

Sediment/Oil/Grease Separator Conveyance Vault w/ Capture Volume Storage

5.4.1. Storage BMPs UDFCD has developed design criteria for sizing volume-based structural BMPs so that

the runoff from approximately 85% of the annual precipitation events is captured and

effectively treated for water quality purposes. The water quality capture volume

(WQCV) refers to a specific depth of precipitation that should be captured by the BMP,

and is a function of the contributing area effective imperviousness and the required

drawdown time of the BMP. Multiplying the WQCV by the contributing area gives the

recommended storage volume for capturing and treating 85% of annual precipitation

events. The procedures used for computing the WQCV are as follows. Note: The

WQCV computed for each BMP does not account for additional storage that may be

required for flood control. Equation (7) is UDFCD’s empirical equation for estimating

the WQCV of a BMP.

)78.019.191.0(* 23 EIEIEIaWQCV (7) Where WQCV = water quality capture volume (watershed-inches), a = coefficient based

on suggested drawdown time for the BMP, and EI = effective imperviousness of the

watershed (%).


40

UDFCD also has procedures for designing the storage volume of EDBs and RPs to

capture and treat the excess urban runoff volume (EURV) for both water quality and flow

control purposes. The EURV is the additional runoff that is generated when undeveloped

land is urbanized and is dependent on the imperviousness and soil type of the watershed.

Equations (7), (9), and (10) are used to compute the EURV for soil types A, B and C/D,

respectively.

)1113.00491.2(*1.1 EIEURV A (8) )0461.02846.1(*1.1 EIEURV B (9) )0339.01381.1(*1.1/ EIEURV DC (10)

Where EURV = excess urban runoff volume (watershed-inches) and EI = effective

imperviousness of the watershed (%).

The design volume of BMPs are then computed using Equation (11) for volume

measured in acre-feet (AF) or Equation (12) for volume measured in cubic feet (ft3).

ASFCAumeStorageVolAFmeDesignVolu **12/)( (11) 560,43***12/)( 3 ASFCAumeStorageVolftmeDesignVolu (12)

Where CA = contributing area (acres), ASF = additional storage factor and

StorageVolume = WQCV or EURV (watershed-inches). Drawdown time (“a”) and

additional storage factor (“ASF”) values for each volume-based BMP in the model are

presented in Table 18. The drawdown time coefficients are values recommended by

UDFCD. The ASF values were determined as described below.

Table 18: Volume-based BMP design factors

BMP Drawdown Time

Coefficient, a Additional Storage

Factor, ASF Extended Detention Basin 1.0 1.2

Retention (Wet) Pond - WQCV 0.8 2.6 Retention (Wet) Pond – EURV 0.8 1.5

Sand Filter Basin 1.0 1.0 Vault w/ Capture Volume 0.8 1.1

Sand Filter Vault 0.8 1.0 Constructed Wetland Basin 0.9 1.75


41

Porous Landscape Detention 0.8 1.0

Extended Detention Basin – additional 20% storage is needed for sediment accumulation

Retention Pond (WQCV) – additional 160% storage is needed for the permanent pool and

sediment accumulation.

Retention Pond (EURV) – additional 50% storage is needed for permanent pool and


Constructed Wetland Basin – additional 75% storage is needed for permanent pool and


Vault with Capture Volume – additional 10% storage is needed for sediment

accumulation.

5.4.2. Conveyance BMPs UDFCD recommends sizing flow-based BMPs to convey the 2-year peak flow rate. The

peak flow rate is computed from the Rational Method, using UDFCD methods for

estimating time of concentration and design rainfall intensity. UDFCD has additional

design criteria for constructed wetland channels (CWC) that must be met after the design

flow rate is determined.

Peak flow rates are estimated from the Rational Method, Equation (13).

CAiCQ ** (13)

Where Q = peak flow rate (cfs), C = runoff coefficient for contributing area, i = rainfall

intensity (in/hr), CA = contributing area (acres).

The rainfall intensity is computed using Equation (14), derived by UDFCD and

applicable to the Front Range region of Colorado.

786.0

1

)10(

5.28

Tc

Pi

(14)

Where P1 = 2-Year, 1-hour point rainfall depth (inches) and Tc = time of concentration

(minutes).


42

The time of concentration is the sum of the travel times for initial (overland) flow, Ti, and

channelized flow, Tt.

TtTiTc (15)

For locations within the Front Range region of Colorado, the travel time for initial

(overland) flow, Ti, is the lesser of the two values computed in Equations (16) and (17).

33.0

5 )1.1(395.0

S

LCTi OF

(16)

10

180 OFL

Ti (17)

Where C5 = runoff coefficient for 5-year frequency, S = watershed slope (ft/ft) and LOF =

overland flow length (ft).

Travel time for channelized flow is computed with Equation (18).

V

LTt CF (18)

Where LCF = channelized flow length (ft) and V = average velocity (ft/s) computed using

Equation (19).

5.0SCV v (19)

Where Cv = conveyance coefficient1 and S = watershed slope (ft/ft).

To minimize the number of required user inputs, the overland and channelized flow

lengths are automatically computed by the model, assuming a square, v-shaped draining

watershed, as shown in Figure 9. These assumed lengths are considered reasonable for

planning-level studies.

1 The conveyance coefficient is assumed to be 20, the value used for paved areas and shallow paved swales which are expected in urban watersheds.


43

Figure 9: Diagram showing overland and channelized flow lengths assuming v-

shaped watershed

Overland and channelized flow lengths are computed using Equations (20) and (21),

respectively.

43560**5.0 CIALOF (20)

43560*CIALCF (21)

Where LOF = overland flow length (ft) (maximum of 300 ft), LCF = channelized flow

length (ft) and CIA = contributing area to the BMP (acres).

5.4.3. Permeable Pavements (PP) The surface area of PPs are input by the user.

5.5. Number of BMPs When applying BMPs to a subcatchment, BMP-REALCOST assumes that no area in that

subcatchment is left untreated, therefore the number of BMPs (N) in each subcatchment

is computed using Equation (22) and rounded to the next highest integer.

CIAICAN T /* (22) where CA = subcatchment total area (acres) and CIA = contributing impervious area

(acres) for BMPs (input by the user) or CIA = (RAPP + SAPP) for PP. To evaluate

Chan

nelized Flow

Length


44

untreated areas in a scenario, the user can select BMP type “None” to be applied to a

subcatchment. Using the regional control option, N =1.

5.6. Construction Costs Construction costs are represented in the form of a parametric equation (23) where costs

are expressed as a function of the size of the BMP, a base cost and an exponent term that

can reflect economies of scale realized with some construction projects.

XUCConCost (23)

Where ConCost = total construction cost, C = base cost, X = unit cost, U = size of the

BMP (ft2, ft3, AF, cfs, acres) and α = economies of scale factor.

The size of the BMP is the storage volume for storage BMPs, design flow rate for

conveyance BMPs and surface area for PPs. This method of computing construction

costs was chosen because it achieves the model objectives of being able to evaluate

multiple BMP sizes within one scenario, is able to reflect economies of scale and is

simple enough for users to adjust the cost equation to fit their needs.

5.6.1. Development of Construction Cost Equations Muller Engineering (2009) developed construction cost estimates for each of the BMPs

included in the model based on UDFCD BMP design criteria and unit costs available

from Denver-area construction projects completed in the past 5 years. For each BMP,

construction costs for three different sizes were estimated. The estimates were adjusted

to May 2008 national average costs using the ENR CCI (ENR CCI = 8141), assuming

that the original estimates were representative of 2008 costs in the Denver region (ENR

CCI = 5782). Plots of BMP cost versus size were created and best-fit lines were applied

to generate a cost equation. The methods and assumptions used to develop the

construction cost estimates are documented in the memorandum prepared by Muller

Engineering (2009), which is included in as Appendix B in this manual. The following

sections present the plots and equations generated for each BMP.


45

Constructed Wetland Basins, Extended Detention Basins and Retention Ponds with Water Quality Control Volume

Figure 10 presents the plots and cost equations generated for constructed wetland basins,

extended detention basins and retention ponds designed for the WQCV.

Figure 10: Cost equations developed for constructed wetland basins, extended detention ponds and retention ponds with WQCV.

Sand Filter Basins, Porous Landscape Detention, Vaults with Capture Volume and Sand Filter Vaults

Figure 11 presents the plots and cost equations generated for sand filter basins, porous

landscape detention, vaults with capture volume and sand filter vaults designed for the

WQCV. Note that the costs for PLDs assume that the PLD is “unconstrained”, meaning

that is does not have concrete sidewalls.

y = 0.8911x + 23897

R2 = 0.9992

y = 0.8881x + 21368

R2 = 1

y = 0.7105x + 23082

R2 = 1

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Storage Volume (ft3)

Co

nst

ruct

ion

Co

st (

$200

8)

EDB CWBRP Linear (EDB)Linear (CWB) Linear (RP)


46

Figure 11: Cost equations developed for sand filter basins, porous landscape detention, vaults with capture volume and sand filter vaults designed for the

WQCV.

Permeable Pavements

Figure 12 presents the plots and cost equations generated for concrete grid pavers (also

known as modular block pavement), permeable interlocking concrete pavers (also known

as cobblestone block pavers), reinforced grass pavement, porous concrete pavement and

porous gravel pavement.

y = 3.5481x + 9860.7

R2 = 0.9994

y = 9.9256x + 10729

R2 = 0.9998

y = 19.487x + 16616

R2 = 0.9986

y = 36.257x + 27046

R2 = 0.997

$0

$20,000

$40,000

$60,000

$80,000

$100,000

$120,000

$140,000

$160,000

$180,000

0 2,000 4,000 6,000 8,000 10,000


Co

nst

ruct

ion

Co

st (

$200

8)

SFB PLD VCV SFVLinear (SFB) Linear (PLD) Linear (VCV) Linear (SFV)


47

Figure 12: Cost equations developed for permeable pavements.

Hydrodynamic Separators, Sediment/Oil/Grease Separators, Media Filter Vaults and Inlet Inserts

Figure 13 presents the plots and cost equations generated for hydrodynamic separators,

sediment/oil/grease separators, media filter vaults2 and inlet inserts3. The construction

costs for inlet inserts assume that each insert has a design flowrate of approximately 0.4

cfs and that each insert costs approximately $856 to install.

2 The costs for media filter vaults are based on two proprietary devices, the EcoStorm Plus and StormFilter. The Filterra system is not representative of the devices being evaluated for this category, therefore its costs were removed from consideration in the model. 3 The costs of inlet inserts are based on two propriety devices, the Ultra Urban Filter with Smart Sponge and the FlexStorm. The Hydroscreen device is not representative of the devices being evaluated for this category, therefore its costs were removed from consideration in the model.

y = 11.822x + 13236

R2 = 1

y = 16.486x + 14409

R2 = 1

y = 10.099x + 102.86

R2 = 1

y = 14.226x + 7257

R2 = 0.9999

y = 6.8713x + 7257.7

R2 = 0.9995

$0

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

Surface Area (ft2)

Co

ns

tru

cti

on

Co

st

($2

00

8)

CGP PICP RGP PCPPGP Linear (CGP) Linear (PICP) Linear (RGP)Linear (PCP) Linear (PGP)


48

Figure 13: Cost equations developed for proprietary devices.

Extended Detention Basins and Retention Ponds with Excess Urban Runoff Volume

Figure 14 presents the plots and cost equations generated for constructed wetland basins,

extended detention basins and retention ponds designed for the EURV.

y = 13337x + 16639

R2 = 0.9952

y = 17960x + 8850.9

R2 = 0.9924

y = 57880x + 30373

R2 = 0.9983

y = 1966.6x + 393.32

R2 = 0.9963$0

$50,000

$100,000

$150,000

$200,000

$250,000

$300,000

0 1 2 3 4 5

Design Flowrate (cfs)

Co

nst

ruct

ion

Co

st (

$200

8)

HS SOG MFV II

Linear (HS) Linear (SOG) Linear (MFV) Linear (II)


49

Figure 14: Cost equations developed for extended detention ponds and retention ponds with EURV.

Constructed Wetland Channel

Construction costs for CWCs are dependent on both the design flowrate of the channel

(which controls the cross sectional area of the channel) and the length of the channel.

Figure 15 shows the relationship of construction costs per 100 linear feet of channel to

the design flowrate.

y = 0.5465x + 26196R2 = 0.998

y = 0.4587x + 27884R2 = 0.9989

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000


Co

nst

ruct

ion

Co

st (

$200

8)

EDB RP Linear (EDB) Linear (RP)


50

Figure 15: Unit construction cost equation developed for constructed wetland channels.

To estimate the total construction costs, the unit cost taken from Figure 15 is then

multiplied by the length of the channel, which is assumed to be equal to the square root of

the area draining to the channel, Equation (24). This assumes that the contributing area is

square and the channel bisects the area as in a classic “V-shaped” watershed model.

560,43*CIAL (24)

Where L = channel length (ft) and CIA = contributing area to the BMP (acres).

5.6.2. Construction Cost Equations Used in Model Table 19 summarizes the default equations used to compute BMP construction cost

estimates in the model. The costs are adjusted to May 2008, nationally-averaged costs

using the Engineering News Record (ENR) Construction Cost Index (CCI) value of 8,141

(ENR 2008). The procedures for adjusting costs using this index are documented in

Sections 5.13 and 5.14.

y = 102.7x + 6700.3

R2 = 0.9964

$0

$2,000

$4,000

$6,000

$8,000

$10,000

$12,000

0 5 10 15 20 25 30 35

Design Flowrate (cfs)

Co

nst

ruct

ion

Co

st/1

00 L

F (

$200

8)

CWC Linear (CWC)


51

Table 19: Summary of construction cost equations used in the model BMP Cost Equation

($2008) Constructed Wetland Basin $21,368 + $0.89(V) Constructed Wetland Channel1 $6,700 + $102.70(F) Extended Detention Basin (WQCV) $23,897 + $0.89(V) Extended Detention Basin (EURV) $26,196 + $0.55(V) Hydrodynamic Separator $16,639 + $13,337(F) Inlet Inserts $393.32 + $1,967(F) Media Filter Vault $30,373 + $57,880(F) Porous Landscape Detention $10,729 + $9.93(V) Retention (Wet) Pond (WQCV) $23,082 + $0.71(V) Retention (Wet) Pond (EURV) $27,884 + $0.46(V) Sand Filter Basin $9,861 + $3.55(V) Sand Filter Vault $27,046 + $36.26(V) Sediment/Oil/Grease Separator $8,851+ $17,960(F) Vault with Capture Volume $16,616 + $19.49(V) Concrete Grid Pavers (Modular Blocks) $102.86 + $10.10(SA) Permeable Interlocking Concrete Pavers (Cobblestone Blocks)

$7,257 + $14.23(SA)

Porous Concrete Pavement $14,409 + $16.49(SA) Porous Gravel Pavement $7,258 + $6.87(SA) Reinforced Grass Pavement $13,236 + $11.82(SA) Notes: 1 - cost per 100 linear feet of channel F = design flowrate (cfs) SA = surface area (ft2) V = storage volume (ft3)

5.7. Land Costs Land costs are a function of the land required for the BMP and the cost of the land on

which the BMP will be constructed. For storage BMPs, the land required can be

computed as a function of the BMP size and a derived coefficient referred to as the “land

consumption coefficient” (CLC), with land costs then being computed using Equation

(25).

CLCULCLandCost ** (25)

Where LandCost = cost of land required for the BMP, LC = cost of land based on land

use ($/acre), U = size of the BMP (ft2, ft3, AF, cfs, acres) and CLC = factor relating the

land required for the BMP to its size (acres/unit).


52

Permeable pavements and BMPs located underground do not have land costs associated

with them.

The land required for constructed wetland channels is equal to the surface area of the

channel, which is the product of the channel top width and length. Land costs for CWCs

are computed using Equation (26).

LTwLCLandCost ** (26)

Where LandCost = cost of land required for the BMP, LC = cost of land based on land

use ($/acre), L = channel length (ft) and Tw = channel top width (ft).

The channel length is determined using Equation (24). The channel top width is

computed using an iterative procedure that solves for the appropriate channel cross-

section area required to convey the design flowrate, as recommended by UDFCD.

5.7.1. Cost of Land Based on Land Use The cost of land is a function of the land use. The default land cost values used in the

model (Table 13) are average values of the ranges reported in Strecker et al (2005) (Table

20) with some modifications for the Denver-region. These costs are considered applicable

for new developments on previously undeveloped land or land on which any existing

structures have minimal value. The costs associated with redevelopment, are likely to be

higher due to the value of structures already existing on that land.

Table 20: Land cost estimates as function of land use

Land Use Land Cost ($/acre) Unimproved Land $25,000 – 50,000

Residential $75,000 – 200,000 Commercial $100,000 – 300,000 High Density $500,000 – 3,000,000


53

5.7.2. Land Required for BMPs (CLC) Recognizing that the area of land required for BMPs is related to the size of the BMP, a

“land consumption coefficient” (CLC) was derived to quantify this relationship based on

UDFCD BMP design recommendations. The following sections describe the methods

and assumptions used to develop this relationship for each BMP that requires land.

Constructed Wetland Basin The CLC for CWBs = 0.00002 acres/ft3, assuming average depth of 2 feet and an area

equal to 75% of the CWB surface area be set aside for maintenance access and other

considerations.

Constructed Wetland Channel The CLC for CWCs = 1 acre/acre, assuming that the land required for CWCs is equal to

the surface area of the BMP. Because the size of CWCs are calculated and reported in

terms of their design flowrate (cfs), the tool computes the surface area of the CWC

internally as a function of the channel top width and channel length.

Extended Detention Basin -WQCV/EURV The CLC for EDBs = 0.000016 acres/ft3, assuming average depth of 2.5 feet and an area

equal to 75% of the EDB surface area be set aside for maintenance access and other

considerations.

Porous Landscape Detention The CLC for PLDs = 0.000023 acres/ft3, assuming that the WQCV can “pond” to a depth

of 1 foot on the surface of the PLD.

Retention Pond -WQCV/EURV The CLC for RPs = 0.000013 acres/ft3, assuming average depth of 3 feet and an area

equal to 75% of the RP surface area be set aside for maintenance access and other

considerations.

Sand Filter Basin


54

The CLC for SFBs = 0.000013 acres/ft3, assuming average depth of 3 feet and an area

equal to 75% of the SFB surface area be set aside for maintenance access and other

considerations.

Underground BMPs Underground BMPs do not consume any land and the CLCs are set equal to 0%.

Table 21 summarizes the CLC values used in the model.

Table 21: CLC values used for computing BMP land costs BMP CLC Units

Constructed Wetland Basin 0.000020 Acres/ft3 Constructed Wetland Channel 1 Acres/acre

Extended Detention Basin-EURV 0.000016 Acres/ft3 Extended Detention Basin-WQCV 0.000016 Acres/ft3

Hydrodynamic Separator 0 Acres/cfs Inlet Inserts 0 Acres/cfs

Media Filter Vault 0 Acres/cfs Permeable Pavements 0 Acres/acre

Porous Landscape Detention 0.000023 Acres/ft3 Retention (Wet) Pond-EURV 0.000013 Acres/ft3 Retention (Wet) Pond-WQCV 0.000013 Acres/ft3

Sand Filter Basin 0.000013 Acres/ft3 Sand Filter Vault 0 Acres/ft3

Sediment/Oil/Grease Separator 0 Acres/cfs Vault w/ Capture Volume 0 Acres/ft3

5.8. Contingency, Engineering and Administration Costs The additional costs attributable to contingencies, engineering, permitting, erosion

control, administration, etc. are assumed to be 40% of the construction costs, as estimated

for Denver-area projects by Urbonas (2008).

5.9. Capital Cost Calculations Capital costs include construction costs, land costs and additional costs attributed to

contingencies, engineering, administration etc., and are computed using Equation (27).

LandCostXUCCEACCost )(*)1( (27)


55

Where CCost = capital cost for an individual BMP, CEA = factor accounting for

contingencies/engineering/administration (%), C = base cost ($), X = unit cost ($ per

unit), U = BMP Size (AF, ft3, ft2, acre, cfs), α = economy of scale factor and LandCost =

land costs ($).

The default values of each variable, for each BMP type, are presented in Table 22.


56

Table 22: Default values of capital cost parameters used in the model BMP CEA (%) C($) X($/unit) Units α CLC

Constructed Wetland Basin 40 $21,368 $0.89 ft3 1 0.000020 Constructed Wetland Channel 40 $6,700 $102.70 ft3 1 1 Extended Detention Basin (WQCV) 40 $23,897 $0.89 ft3 1 0.000016 Extended Detention Basin (EURV) 40 $26,196 $0.55 ft3 1 0.000016 Hydrodynamic Separator 40 $16,639 $13,337 cfs 1 0 Inlet Inserts 40 $393.32 $1,967 cfs 1 0 Media Filter Vault 40 $30,373 $57,880 cfs 1 0 Porous Landscape Detention 40 $10,729 $9.93 ft3 1 0.000023 Retention (Wet) Pond (WQCV) 40 $23,082 $0.71 ft3 1 0.000013 Retention (Wet) Pond (EURV) 40 $27,884 $0.46 ft3 1 0.000013 Sand Filter Basin 40 $9,861 $3.55 ft3 1 0.000013 Sand Filter Vault 40 $27,046 $36.26 ft3 1 0 Sediment/Oil/Grease Separator 40 $8,851 $17,960 cfs 1 0 Vault with Capture Volume 40 $16,616 $19.49 ft3 1 0 Concrete Grid Pavers 40 $102.86 $10.10 ft2 1 0 Permeable Interlocking Concrete Pavers 40 $7,257 $14.23 ft2 1 0 Porous Concrete Pavement 40 $14,409 $16.49 ft2 1 0 Porous Gravel Pavement 40 $7,258 $6.87 ft2 1 0 Reinforced Grass Pavement 40 $13,236 $11.82 ft2 1 0


57

5.10. Maintenance Cost Calculations As with capital costs, it was preferred to develop cost equations that related annual

maintenance costs to the size of the BMP. Annual maintenance costs for a single BMP

typically reflect the costs of performing a wide variety of activities. Those activities can

generally be divided into two types; those with costs that vary according to the size of the

BMP (“variable” maintenance costs) and those that do not (“constant” maintenance

costs). Equation (28) was developed for estimating annual maintenance costs as a

function of multiple maintenance activities in both types.

UCCMCost VC * (28)

Where U = BMP Size (AF, ft3, ft2, acre, cfs), MCost = annual maintenance costs, CC =

annual cost for all “constant” maintenance activities and CV = annual unit cost for all

“variable” maintenance activities.

Table 23 shows the maintenance cost equations developed for each BMP. The methods

and assumptions used to develop the cost equation are explained in Appendix C.

Table 23: Annual maintenance cost equations BMP CC($) CV($/unit) Units

Constructed Wetland Basin $0 $1,956 AF Constructed Wetland Channel $0 $960 Acre Extended Detention Basin (WQCV) $1,849 $2,782 AF Extended Detention Basin (EURV) $1,849 $2,782 AF Hydrodynamic Separator $0 $749 cfs Inlet Inserts $165 $0 cfs Media Filter Vault $0 $835 cfs Porous Landscape Detention $0 $0.62 CF Retention (Wet) Pond (WQCV) $1,521 $1,598 AF Retention (Wet) Pond (EURV) $1,521 $1,598 AF Sand Filter Basin $0 $1,096 AF Sand Filter Vault $0 $1.86 CF Sediment/Oil/Grease Separator $0 $832 cfs Vault with Capture Volume $0 $0.66 CF Concrete Grid Pavers $0 $125 Acre Permeable Interlocking Concrete Pavers $0 $125 Acre Porous Concrete Pavement $0 $125 Acre Porous Gravel Pavement $0 $5,647 Acre Reinforced Grass Pavement $0 $4,040 Acre


58

5.11. Rehabilitation/Replacement Cost Calculations Rehabilitation/replacement costs are computed as percentage of the original construction

costs of the BMP using Equation (29).

ConCostRRCost * (29)

Where RCost = rehabilitation/replacement costs for an individual BMP, R = percentage

of construction costs and ConCost = construction costs of BMP.

5.11.1. Reoccurrence Interval of Rehabilitation/Replacement Costs Rehabilitation and replacement costs reoccur at time intervals equal to the expected

design life of each BMP. With a few exceptions (described below), the design life

assumed in the model is based on the average of a range of values of expected design

lives reported by USDOT (2002).

Inlet Inserts

The estimated design life of two common inlet inserts is reported to be 1-3 years on

average, therefore replacement is assumed to occur every 2 years in the model.

Hydrodynamic Separators and Sediment/Oil/Grease Separators

The design life for “manufactured systems” reported in USDOT (2002) is assumed to

represent those structures that are primary constructed with precast concrete. However,

the HSs and SOGs in this model are assumed to be representative of the more recent

proprietary models that include relatively sophisticated hydraulic controls and screens

constructed of steel or some other metallic material. These materials do not last as long

as concrete, therefore a design life of 25 years is assumed in this model.

5.11.2. Rehabilitation/Replacement Costs as a Percentage of Construction Costs

There was no information reported in the literature for rehabilitation and replacement

costs of BMPs, therefore estimates of costs as a percentage of the original construction

costs were made using best engineering judgment. The assumptions made to do so are

explained in the following paragraphs.


59

Large, Aboveground BMPs with Extensive Infrastructure

The BMPs that fall under this category include constructed wetland basins, constructed

wetland channels, extended detention basins and retention ponds. The majority of

construction costs can be attributed to excavation and installation of infrastructure such as

berms, wingwalls, grade controls, outlet structures, etc. Once the design lives of these

BMPs are exceeded, it is assumed that most of the installed infrastructure will require

rehabilitation and/or replacement. Replacing these items is assumed to cost

approximately 80% of the original construction costs. The 20% savings from the original

construction costs is assumed to come from not requiring extensive re-excavation. Note

that these costs do not include the costs of sediment removal, which usually occurs more

frequently, and is included as a maintenance cost in this model.

“Filtering” BMPs

“Filtering” BMPs include porous landscape detention, sand filter basins and sand and

media filter vaults. Most of the construction costs of these BMPs can be attributed to

excavation and installation of the filtering media. Once the design life of these BMPs is

exceeded, it is assumed that the filtering media would need to be removed and replaced at

a cost equal to the original construction cost. This assumes that removal of the filtering

media would require a similar effort as the original excavation and installation of new

media would be similar to the original media installation effort.

Belowground BMPs

The BMPs that fall under this category are hydrodynamic separators, sediment/oil/grease

separators, and vaults with capture volume. Much of the original construction costs can

be attributed to excavation, device procurement and installation. Once the design life of

these BMPs is exceeded, it is assumed that they must be completely removed and new

devices installed, at a cost of approximately 120% of the original construction costs. The

additional 20% of costs is assumed to account for additional effort needed to remove and

dispose of the existing device. The costs of excavation, procurement and installation of

the new device are assumed to be similar to the original costs.


60

Inlet Inserts

The costs of replacing inlet inserts are assumed to be similar to the original costs which

primarily include procurement and installation.

Permeable Pavements

The construction costs of permeable pavements can mostly be attributed to grading of the

site and installation of the subbase and pavement material. At the end of the design life,

it is assumed that replacement of the pavement would include demolition/removal and

replacement of the pavement material at a cost of approximately 80% of the original

construction costs.

Table 24 presents the percentage value and cost reoccurrence interval for each BMP.

Table 24: Rehabilitation/replacement cost percentages and frequency estimates BMP Frequency

(years) Cost

(as % of construction costs) Constructed Wetland Basin 35 80% Constructed Wetland Channel 35 80% Extended Detention Basin (WQCV) 35 80% Extended Detention Basin (EURV 35 80% Hydrodynamic Separator 25 120% Inlet Inserts 2 100% Media Filter Vault 12 100% Porous Landscape Detention 12 100% Retention (Wet) Pond (WQCV) 35 80% Retention (Wet) Pond (EURV) 35 80% Sand Filter Basin 8 100% Sand Filter Vault 12 100% Sediment/Oil/Grease Separator 25 120% Vault with Capture Volume 75 120% Concrete Grid Pavers 18 80% Permeable Interlocking Concrete Pavers 18 80% Porous Concrete Pavement 18 80% Porous Gravel Pavement 18 80% Reinforced Grass Pavement 18 80%

5.12. Administrative Cost Calculations Administrative costs are calculated using the following equation (30).

MCostDIACost * (30)


61

Where ACost = annual administrative costs for an individual BMP, I = annual

compliance inspection costs, D = percentage (of annual maintenance costs) and MCost =

annual maintenance costs.

Annual compliance inspection costs were estimated to be approximately $19 per BMP

per year (see Appendix C for details). The percentage of annual maintenance costs is

assumed to be 12%.

5.13. Cost Adjustments for Time Cost data reported in the literature were adjusted for inflation to May 2008 dollars using

Equation (31) with the 20-city average value of the ENR CCI (ENR 2008). Table 25

presents average annual 20-city ENR CCI values from 1986 to 2008.

)(

)()()(

presentENRCCI

yearbaseENRCCIyearbaseCostpresentCost (31)

Table 25: Engineering News Record 20-City construction cost index (1986-2008)

Year 20-City ENR CCI Year 20-City ENR CCI 1986 4295 1998 5920 1987 4406 1999 6059 1988 4519 2000 6221 1989 4615 2001 6334 1990 4732 2002 6538 1991 4835 2003 6695 1992 4985 2004 7115 1993 5210 2005 7446 1994 5408 2006 7888 1995 5471 2007 8089 1996 5620 May 2008 8141 1997 5826

Source: ENR (2008)

5.14. Cost Adjustments for Location Cost data can also be adjusted for location to account for regional differences in

construction costs (materials, labor, etc.). Along with the 20-city nationally-averaged

index, ENR also publishes regional indices for 20 cities in the United States. These

indices adjust costs from the 20-city nationally-averaged costs using Equation (32).


62

Table 26 presents the regional index and factor for each city for May 2008. The regional

factor can vary over time however it is generally consistent over short time periods.

Recently, the regional factor for Denver has been in the range of 0.7-0.75. This factor is

useful for determining the regional ENR CCI when only the 20-City average ENR CCI is

available.

)(

)()()(

nationalENRCCI

regionalENRCCInationalCostregionalCost

(32)

Table 26: Engineering News Record regional cost indices (May 2008)

City Regional CCI Regional Factor (Regional/National)

20-City average 8141 - Atlanta 5290 0.65

Baltimore 5537 0.68 Birmingham 5535 0.68

Boston 10004 1.23 Chicago 11176 1.37

Cincinnati 7602 0.93 Cleveland 8555 1.05

Dallas 5005 0.61 Denver 5782 0.71 Detroit 9071 1.11

Kansas City 9303 1.14 Los Angeles 9224 1.13 Minneapolis 9620 1.18 New Orleans 4549 0.56

New York 12482 1.53 Philadelphia 9874 1.21 Pittsburgh 7617 0.94 St. Louis 8769 1.08

San Francisco 9174 1.13 Seattle 8642 1.06

Source: ENR (2008)

5.15. Net Present Cost Calculations The net present costs (NPC) for all BMPs in a subcatchment, k, is computed using as

,

1 , ,

, , , ,

11

(33)


63

where N = number of BMPs, CEA = contingencies/engineering/administrative costs (%),

CCost = construction costs ($), LCost = land costs ($), RCost =

rehabilitation/replacement costs ($), MCost = operation and maintenance costs ($), ACost

= admininstrative/management costs ($), PH = planning horizon (yrs), IRf = average

inflation rate (%)/100, RORf = average rate of return (%)/100, y = time from present (yrs),

subscript n denotes the specific BMP type and subscript k denotes the individual

subcatchment. RDF is the rehabilitation cost discount factor (unitless) that “discounts”

rehabilitation costs in years when the design life of the rehabilitated BMP exceeds the

number of years remaining in the planning horizon, thus ensuring that the same number

of years are used for both cost and benefit calculations. RDF is computed as

,

1

1

1 1

1

1

(34)

Where DL = design life of the BMP (years).

The NPC for a complete scenario with BMPs in multiple subcatchments is computed as

K

kkK NPCNPC

1

(35)

where K = number of subcatchments. If a regional BMP is being evaluated for the

scenario, then k = K = 1, reflecting that costs are computed for one BMP only.

5.15.1. Inflation Rate The inflation rate describes how the costs for maintenance, administration, and

rehabilitation/replacements will increase in the future. The average long-term inflation

rate for these activities was estimated by evaluating the annual change in the 20-city

average ENR CCI. Over the past 50 years, the 20-city average ENR CCI has increased

from 759 in 1958 to 8141 in May 2008 (ENR 2008). During that time, the average

annual increase in ENR CCI was 4.6%.


64

5.15.2. Planning Horizon The planning horizon of a project defines the time over which the net present value of the

project costs will be evaluated. A planning horizon of 50 years is recommended by

UDFCD and other water resource organizations, recognizing the longevity of such

projects and the difficulty in financing their construction.

5.15.3. Rate of Return The rate of return (ROR) describes how monies that are set aside (invested) in the present

day will appreciate in the future. The future worth of these investments can then be used

to pay for future costs such as maintenance and administration. There was no

information in the literature documenting typical ROR values for municipalities and/or

stormwater management agencies, therefore a rough estimate of 5% was assumed.

5.16. BMP Effectiveness Calculations This model evaluates the effectiveness of BMPs using two different measures:

1. The reduction in annual runoff volume discharged to the receiving waters and,

2. The reduction in annual pollutant loading to the receiving waters

As explained in the following sections, both measures are computed in accordance with

Strecker et al’s (2001) recommendations for evaluating the effectiveness of BMPs.

5.16.1. Runoff Volume Reduction Runoff volume reduction RVR (ft3/yr) is computed for each subcatchment k by

kkk RVRWRVTRVR (36)

where RVT = total volume of runoff generated from a subcatchment (ft3/yr) and RVRW =

the volume of runoff discharged to the receiving water (ft3/yr). RVT (ft3/yr) is computed

by multiplying the average annual runoff depth, estimated using the Simple Method

(Schueler 1987), by the subcatchment area

kkTk CARCPjPRVT *** , (37)


65

where P = annual precipitation depth (in), Pj = fraction of annual storms producing

runoff (value = 0.9 assuming 90% of annual precipitation produces runoff), RCT

(unitless) is the 2-year runoff coefficient computed using the subcatchment total

imperviousness, and CA is the subcatchment total area (acres).

The total volume of runoff that reaches the inlet of downstream BMPs, RVINT (ft3/yr),

can be computed by

kkEkT CARCPjPRVIN *** ,, (38)

where RCE = 2-year runoff coefficient computed using the subcatchment effective

imperviousness, which accounts for volume reduction due to source controls in the

subcatchment.

Runoff that reaches the inlet of downstream BMPs is either fully treated by the BMP or

bypasses full treatment when the BMP capacity is exceeded. The volume of runoff that

receives full treatment, RVINF (ft3/yr), and the volume that bypasses treatment, RVINB

(ft3/yr), can be computed using Equations (39) and (40)

100/*,, nkTkF RVINRVIN (39)

/100)λ(1*RVINVINR nkTkB ,, (40)

where λn = BMP capture efficiency (%) for a BMP type n (Table 11). For storage BMPs

designed to capture the WQCV and EURV, λ = 85% and 98% respectively. The former

value is derived from the fundamental basis of the WQCV which is to capture 80-90% of

the average annual runoff (UDFCD 2004) and the latter value from UDFCD modeling

EURV results (UDFCD unpublished data). No studies could be found documenting λ for

conveyance BMPs, therefore BMP-REALCOST uses λ = 85% assuming that those BMPs

are designed to effectively treat the same number of storms as storage BMPs designed for

the WQCV. Methods for estimating λ for PPs are described below.

Finally, RVRW (ft3/yr) is computed as

kB,nkFk RVIN/100)θ(1*VINRVRWR , (41)

where θn = is the percentage of RVINF that is removed from the surface water system via

infiltration and/or evapotranspiration in BMP type n (Table 11). θ values are defined for


66

storage and conveyance BMPs based on the findings of Strecker et al (2005) who

reported values for the ratio of measured inflow/measured outflow for several BMPs

using data contained in the International BMP Database and UDFCD (unpublished data)

who estimated the same ratios for other BMPs. The methods used to derive θ values for

PPs are described below.

If a regional BMP is being evaluated, then RCT and RCE in equations (37) and (38),

respectively, are area-weighted values for all of the subcatchments and CA (in the same

equations) is the sum of all subcatchment contributing areas; such that the calculated

value of RVT is the total runoff volume generated from all subcatchments and RVIN is the

runoff volume reaching the regional BMP.

Permeable Pavement Capture Efficiency and Runoff Volume Reduction Capture Efficiency Very few studies have been conducted to assess the capture efficiency of permeable pavements. Those studies that have were limited to only a few of types of permeable pavements with no impervious runon area and were conducted in regions (southeast and northwest US) with very different hydrology than Colorado. Given the lack of applicable field data, PP capture efficiencies were estimated based on experience and engineering judgment. Field experiences have shown that PPs have considerable infiltration capacity (at times exceeding tens or hundreds of inches per hour), enough to safely assume that 100% of runoff would be captured when the impervious runon area:PP area (RAPP:SAPP) ratio is less than or equal to 5:1 (the maximum recommended for use in this model). However, experiences have also shown that incorrect construction (e.g. inadequate grading, “oversmoothing” of porous concrete, etc.) in some portions of the installation can result in some runoff being generated from PP installations. The extent of those construction errors has not been quantified, however using engineering judgment we have reasoned that construction errors may result in up to 5% of the annual runoff not being adequately captured on a PP area with no runon area. Assuming the volume of runoff not captured due to construction errors would increase linearly as the RAPP:SAPP ratio was increased, the following equation was developed to estimate the capture efficiency of PPs under RAPP:SAPP ratios less than or equal to 5:1. The equation reflects a maximum capture efficiency of 95% assuming no impervious runon area, declining linearly with increasing RAPP:SAPP ratios.

λ = min(100% - (RAPP/SAPP)*5%, 95%) Runoff Volume Reduction If the PP is designed to infiltrate all captured runoff, then 100% of the captured runoff will infiltrate and be removed from the surface water system. If the PP is underdrained, then a certain percentage of the infiltrated water will be underdrained and the remaining


67

percentage will be removed from the surface water system via infiltration (if subbase is unlined) and/or ET. Unpublished data collected from UDFCD, using two different PP types with a 3:1 runon:PP area ratio, suggests that approximately 40% of the captured runoff is lost due to infiltration and/or ET in unlined, underdrained systems. It should be noted that these installations contained sand filter layer approximately 6” thick. Intuitively, that percentage might increase with lower runon:PP ratios and decrease with higher runon:PP ratios, with some minimum value (~10%) that always occur due to water retention in the subbase pore space. The following function is used to estimate the percentage (θ) of infiltrate that is lost to infiltration and/or ET;

θ = max(50% - (RAPP/SAPP)*3%, 10%)

5.16.2. Pollutant Load Reduction Pollutant load reduction, PLR (lb/yr), for a subcatchment k and pollutant m is computed

as

mkmkm k, PLRWPLTPLR ,, (42)

where PLT = total pollutant load generated from the subcatchment (lb/yr) and PLRW =

pollutant load discharged to the receiving water (lb/yr). PLT is given by

mkmkmk, EMCLURVTPLT ,, * (43)

where RVT = total runoff volume generated from the subcatchment (ft3/yr) and EMCLU =

pollutant event mean concentration (mg/L) assigned to the subcatchment land use

classification (Table 27). These values are derived from UDFCD reported values and

information provided by Maestre et al (2005), as documented in Appendix A.

Table 27: Land use average EMCs in stormwater runoff for Denver, CO Constituent Units Industrial Commercial Residential Undeveloped

Total Suspended Solids mg/L 399 225 240 400 Total Nitrogen mg/L 2.7 3.3 3.4 3.4

TKN mg/L 1.8 2.3 2.7 2.9 Nitrate + Nitrite mg/L 0.91 0.96 0.65 0.50

Total Phosphorus mg/L 0.43 0.42 0.65 0.40 Dissolved Phosphorus mg/L 0.20 0.15 0.22 0.10

Copper, Total μg/L 84 43 29 40 Copper, Dissolved μg/L 32 19 17 23

Lead, Total μg/L 130 59 53 100 Lead, Dissolved μg/L 26 16 13 25

Zinc, Total μg/L 520 240 180 100 Zinc, Dissolved μg/L 292 95 78 43


68

Source: UDFCD (2004) with modifications using Maestre et al (2005)

Similar to runoff volume, the pollutant load discharged to the receiving water is the sum

of the “fully-treated” load and the “bypassed” load. Bypassed runoff is assumed to retain

the concentrations of pollutants as generated from the subcatchment (EMCLU), whereas

runoff treated by a BMP type n has effluent concentrations (EMCeff) unique to that BMP.

Accordingly, PLRW (lb/yr) is computed as

mn,nkFmkkBmk, EMCeff*/100)θ(1RVINEMCLURVINPLRW ** ,,, (44)

where RVINB = runoff volume that bypasses BMP treatment (ft3/yr), EMCLU = pollutant

event mean concentration (mg/L) assigned to the subcatchment land use classification,

RVINF = runoff volume that received full BMP treatment (ft3/yr), θn = is the percentage

of RVINF that is removed from the surface water system via infiltration and/or

evapotranspiration in BMP type n and EMCeff = pollutant event mean concentration

(mg/L) assigned to the particular BMP type (Table 28). Geosyntec Consultants and

Wright Water Engineers (2008) have reported median values of effluent EMCs from a

variety of structural BMPs using data contained within the International Stormwater

BMP Database. With some modifications and assumptions (described in Appendix A),

the model uses the reported values for EMCeff values from each BMP.

If a regional BMP is being evaluated PLTm is the sum of PLTk,m for all subcatchments;

RVINB,k and RVINF,k are computed using RVIN for a regional BMP (as discussed at the

end of the Runoff Volume Reduction section of this paper); and EMCLUk m is the volume-

weighted average EMC for runoff from all subcatchments for pollutant m.

5.16.3. Cost Effectiveness The unit cost of reducing pollutant loads, CPLR ($/lb) and runoff volume, CRVR ($/ft3),

for an entire scenario (i.e. all subcatchments, k) over the planning horizon (PH) of a

project can be computing using equations (45) and (46), respectively.


69

K

kmkkm PHPLRNPCCPLR

1, *

(45)

K

kkk PHRVRNPCCRVR

1

* (46)

where NPC = net present costs ($), PLR = pollutant load reduction ($/lb), subscript m

denotes the pollutant, RVR = runoff volume reduction (ft3/yr), PFR = peak flow reduction

(ft3/yr).


70

Table 28: BMP Effluent EMCs used in the model BMP Total

Suspended Solids (mg/L)

Total Phosphorus

(mg/L)

Total Nitrogen(mg/L)

Total Kjeldahl Nitrogen (mg/L)

Total Zince

(mg/L)

Dissolved Zinc

(mg/L)

Total Lead

(mg/L)

Dissolved Lead

(mg/L)

Total Copper(mg/L)

Dissolved Copper (mg/L)

Constructed Wetland Basin

17.77 0.14 1.15 1.05 0.03071 0.01791 0.00326 0.00087 0.00423 0.00736

Constructed Wetland Channel

37.25 0.37 1.91 1.35 0.03071 0.01790 0.00875 0.00087 0.00423 0.00736

Extended Detention Basin

31.04 0.19 2.72 1.89 0.06020 0.02584 0.01577 0.00206 0.01210 0.00737

Hydrodynamic Separator

49.96 0.28 1.48 0.94 0.07212 0.05480 0.00428 0.00195 0.01180 0.02350

Inlet Inserts 38.00 0.12 0.70 1.90 0.09867 0.06867 0.00663 0.00077 0.01370 0.00872 Media Filter Vault 15.86 0.14 0.76 1.55 0.03763 0.05125 0.00376 0.00118 0.01025 0.00900 Porous Landscape Detention

23.92 0.34 0.78 1.51 0.03983 0.02540 0.00670 0.00196 0.01066 0.00840

Retention (Wet) Pond

13.37 0.12 1.43 1.09 0.02935 0.03286 0.00532 0.00248 0.00636 0.00473

Sand Filter Basin 15.86 0.14 0.76 1.55 0.03763 0.05125 0.00376 0.00118 0.01025 0.00900 Sand Filter Vault 15.86 0.14 0.76 1.55 0.03763 0.05125 0.00376 0.00118 0.01025 0.00900 Sediment/Oil/Grease Separator

41.80 1.27 2.07 1.48 0.14025 0.19175 0.01220 0.00227 0.01278 0.01365

Vault with Capture Volume

31.04 0.19 2.72 1.89 0.06020 0.02584 0.01577 0.00206 0.01210 0.00737

Source: International BMP Database (Geosyntec Consultants and Wright Water Engineers 2008 and 2009)


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Table 29: Summary of BMPs that provide peak flow attenuation BMP Peak Flow Attenuation

Constructed Wetland Basin Yes Constructed Wetland Channel Yes

Extended Detention Basin (WQCV) Yes Extended Detention Basin (EURV Yes

Hydrodynamic Separator No Inlet Inserts No

Media Filter Vault No Porous Landscape Detention Yes

Retention (Wet) Pond (WQCV) Yes Retention (Wet) Pond (EURV) Yes

Sand Filter Basin Yes Sand Filter Vault No

Sediment/Oil/Grease Separator No Vault with Capture Volume Yes

BMP-REALCOST User’s Manual and Documentation

72

6. REFERENCES AbTech Industries (2009). “Ultra Urban Filter with SmartSponge Brochure and Technical Specifications.” <http://www.geoproductsinc.com/sales%20brochures/Ultraurban_filters_brochure&spec.pdf>. (Accessed August 2009). ADS (2009). “FlexStorm Inlet Filters”. <http://www.inletfilters.com/>. (Accessed August 2009). Contech (2009). “Operation and Maintenance Guidelines for CatchBasin StormFilter”. < http://www.contech-cpi.com/media/assets/asset/file_name/490/op_maint_sf_cb.pdf>. (Accessed August 2009). Engineering News Record. (2008). “Construction Cost Index History.” <http://enr.construction.com/economics/historical_indices/default.asp>. (Accessed August 2008). Geosyntec Consultants, Urban Drainage and Flood Control District and American Society of Civil Engineers. (2002). “Urban Stormwater BMP Performance Monitoring.” EPA-821-B-02-001. Prepared for USEPA Office of Water. Washington, D.C. Geosyntec Consultants and Wright Water Engineers. (2008). “Analysis of Treatment System Performance - International Stormwater Best Management Practices Database (1999-2008).” Prepared for Water Environment Research Foundation, American Society of Civil Engineers, US Environmental Protection Agency, Federal Highway Administration and American Public Works Association. Maestre, A., Pitt, R., and Center for Watershed Protection. (2005). “The National Stormwater Quality Database, Version 1.1. A Compilation and Analysis of NPDES Stormwater Monitoring Information.” Prepared for USEPA, Office of Water. Washington D.C. Muller Engineering. (2009). “Permanent BMP Construction Cost Estimates Memorandum.” Lakewood, CO. National Weather Service (2008). Climate Report Summary for Denver/Boulder, CO. <http://www.crh.noaa.gov/bou/include/showProduct.php?product=annsum08.txt> (Accessed July 2008). Newnan, Donald, G. (1996). Engineering Economic Analysis. Engineering Press. San Jose. Sixth Edition.

BMP-REALCOST User’s Manual and Documentation

73

Schueler, T. (1987). “Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban Best Management Practices.” Metropolitan Washington Council of Governments, Washington, D.C. Strecker, E.W., Quigley, M.M., Urbonas, B.R., Jones, J.E., Clary, J.K. (2001). “Determining Urban Storm Water BMP Effectiveness.” Journal of Water Resources Planning and Management, 127(3), 144-149. Strecker, E., Huber, W., Heaney, J., Bodine, D., Sansalone, J., Quigley, M., Leisenring, M., Pankani, D., and Thayumanavan, A. (2005). “Critical Assessment of Stormwater Treatment and Control Selection Issues.” Water Environment Research Foundation, 02-SW-1. Alexandria, VA. Urban Drainage and Flood Control District (UDFCD). (2004). Urban Storm Drainage Criteria Manual, Volumes 1-3. Denver, CO. USDOT. (2002). “Stormwater Best Management Practices in an Ultra Urban Setting: Selection and Monitoring. Final Selection Phase.” <http://www.fhwa.dot.gov/environment/ultraurb/uubmp6p4.htm#s651> (Accessed May 2009).

A. Methods and assumptions used to determine land use and BMP effluent event mean concentrations

A-2

This appendix documents how land use and BMP effluent event mean

concentrations were identified for use in the model.

A.1. Land Use Event Mean Concentrations UDFCD (UDFCD 2004) has reported average land use EMC values for 13

constituents in urban stormwater from four different land uses in the Denver, Colorado

metropolitan region (Table A-1) It is recognized that the data from which these value

were estimated were highly variable from site to site and event to event, however over the

long term they may be expected to be reasonably accurate and thus are used in the model.

Table A-1: Land Use Average EMCs for Denver Metropolitan Area

Constituent Units Industrial Commercial Residential UndevelopedTotal Suspended Solids mg/L 399 225 240 400 Total Nitrogen mg/L 2.7 3.3 3.4 3.4 TKN mg/L 1.8 2.3 2.7 2.9 Nitrate + Nitrite mg/L 0.91 0.96 0.65 0.50 Total Phosphorus mg/L 0.43 0.42 0.65 0.40 Dissolved Phosphorus mg/L 0.20 0.15 0.22 0.10 Copper, Total μg/L 84 43 29 40 Lead, Total μg/L 130 59 53 100 Zinc, Total μg/L 520 240 180 100 Source: Table SQ-5 (UDFCD, 2004)

UDFCD did not provide values for dissolved zinc, dissolved lead and dissolved

copper for each land use, therefore ratios of the total recoverable/dissolved fractions of

each metal were estimated based on analyses performed by Maestre and Pitt (2005) on

data contained in the National Stormwater Quality Database (NSQD), Version 1.1. The

results of their analysis are summarized in Table A-2

A-3

Table A-2: Computed total:dissolved metals fractions based on values reported in

the National Stormwater Quality Database, Version 1.1

Constituent Industrial Commercial Residential Lead 4.98:1 3.6:1 4:1 Copper 2.6:1 2.25:1 1.71:1 Zinc 1.78:1 2.54:1 2.32:1

There were no dissolved values reported for undeveloped or open space in the

NSQD, therefore the total:dissolved fractions computed for residential land use was

applied for undeveloped land use also.

A.2. BMP Effluent Event Mean Concentrations

The primary source of data for these values was the Analysis of Treatment

Performance Report (report) (Geosyntec Consultants & Wright Water Engineers 2008),

which reports expected BMP effluent EMCs based on statistical analyses of the data in

the International BMP Database (database) (Geosyntec Consultants & Wright Water

Engineers 2009). The data were analyzed using two methods, one method weighs the

average results from each individual BMP equally and reports “Median of Average

Effluent EMC” values and another method weighs each individual event equally

(potentially putting more weight on the results from one specific BMP which was

thoroughly monitored) and reports “Median of Effluent EMC” values. The first method

that provides “Median of Average Effluent EMC” values is a better indicator of how well

a particular type of BMP may be expected to perform across a variety of sites, and those

values (with a few exceptions discussed below) are used in the model. However, effluent

EMC values were not reported for all of the BMPs included in the model, therefore some

additional analyses and assumptions were necessary.

A-4

When additional analyses were required, first the BMP codes and descriptions

included in the database were used to sort which specific BMPs fell under each BMP

category. Second the names of each specific BMP were cross-referenced within the

“Statistical Summary_wo_WSDOT.xls” spreadsheet (developed by the database team

and available at

<http://www.bmpdatabase.org/ResearchToolsMasterDB.htm#StatSummary> and the

“raw outflow mean [EMC]” value for each constituent was found. Last, the median of all

reported average EMC values for each BMP was computed, thus giving the “Median of

Average Effluent EMC” value that is used in the model.

The following paragraphs explain what values are used for each BMP and the

justification for doing so.

A.2.1. Vault w/ Capture Volume

The report does not provide results specifically for this BMP, however data

collected from these BMPs were included in the analyses for the “Detention Basin”

category, therefore the model uses the EMC values reported for that category.

A.2.2. Constructed Wetland Basin

EMC values reported for “Wetland Basins” are used in the model, with the

following exceptions:

Dissolved Zinc – the data set was insufficient to compute a “Median of

Average Effluent EMC” value for this constituent, therefore the value

A-5

reported using the “Median of Effluent EMC” method (17.90 μg/L) is

used.

Dissolved Copper – the data set was insufficient to compute a “Median of


reported using the “Median of Effluent EMC” method (7.36 μg/L) is used.

A.2.3. Constructed Wetland Channel

EMC values reported for “Wetland Channels” are used in the model, with the

following exceptions:

Total Zinc – the data set was insufficient to compute a “Median of


reported for Constructed Wetland Basins (30.71 μg/L) is used.

Dissolved Zinc – the data set was insufficient to compute a “Median of


reported using the “Median of Effluent EMC” method (17.90 μg/L) for is

used.

Dissolved Lead – the data set was insufficient to compute a “Median of


reported for Constructed Wetland Basins (0.87 μg/L) is used.

Total Copper – There is no reported values for this constituent, therefore

the value reported for Constructed Wetland Basins (4.23 μg/L) is used.

A-6

Dissolved Copper – There is no reported value for this constituent and the

data set for Constructed Wetland Basins was insufficient to compute a

“Median of Average Effluent EMC” value for this constituent, therefore

the value reported using the “Median of Effluent EMC” method (7.36

μg/L) for Constructed Wetland Basins is used.

A.2.4. Extended Detention Basin

Extended detention basins were included within the category “Detention Basins”,

therefore the EMC values reported for that category are used in the model.

A.2.5. Sand Filter Vault

Data collected from sand filter vaults were analyzed under the category “Media

Filter”, along with several other filtering-type BMPs. In an attempt to differentiate

between the different types of BMPs, EMC values were computed for the following

BMPs which were categorized as “Sand Filters” in the database: 5/78, Eastern SF, La

Costa PR, Lakewood Sand Filter, Parkrose SF, Sand Filter and Termination. Table A-3

summarizes the data retrieved and computed average effluent value.

A.2.6. Media Filter Vault

Data collected from media filter vaults were analyzed under the category “Media Filter”,

along with several other filtering-type BMPs. In an attempt to differentiate between the

different filtering BMPs, EMC values were computed for the following BMPs which

were categorized either “Combination of Media or Layered Media Filter”, “Compost

Mixed with Sand”, “Peat Mixed with Sand” or “Other Media Filter” in the database:

A-7

Table A-3: Summary of sand filter data obtained from the International BMP

Database

Parameter # of BMPs # of Samples

Median of Average Outflow EMC

Units

Total Suspended Solids 7 83 10.25 mg/L Total Phosphorus 6 66 0.13 mg/L

Total Nitrogen 5 63 0.80 mg/L Total Kjeldahl Nitrogen 6 66 1.44 mg/L

Total Zinc 7 90 34.56 μg/L Dissolved Zinc 5 62 25.85 μg/L

Total Lead 5 63 1.37 μg/L Dissolved Lead 5 63 1.03 μg/L Total Copper 6 66 9.56 μg/L

Dissolved Copper 6 66 8.25 μg/L

BMP 57, Tree Filter, Bioretention System (D1), Lakewood, MCTT Filtering Chamber,

Via Verde, Compost 1 and Hal Marshall Bioretention Cell. Table A-4 summarizes the

data retrieved and computed average effluent value.

Table A-4: Summary of media filter data obtained from the International BMP

Database



Units






A-8

A.2.7. (U) Hydrodynamic Separator

Although values are reported for “hydrodynamic devices” in the Analysis of

Treatment Performance Report (Geosyntec Consultants & Wright Water Engineers

2008), the analysis included some devices (i.e. treatment trains, up-flow devices, etc.)

that do not adequately represent the devices that are being simulated in the model. Data

from the following BMPs were used to compute the values summarized in Table A-5:

Addison-Wesley Interceptor, Aqua Swirl, Continuous Deflectie Separation, Continuous

Deflective Separation Unit, Filmore CDS, Vortechnics, Vortechnics Model 11000 and

Vortechs No 5000.

Table A-5: Summary of hydrodynamic separator data obtained from the

International BMP Database



Units

Total Suspended Solids 8 116 47.28 mg/L Total Phosphorus* 5 133 0.20 mg/L




Dissolved Copper 2 23 25.21 μg/L (*) one BMP was not included due to an unusually high value - possibly input error

A.2.8. (U) Sediment/Oil/Grease Separator

The Analysis of Treatment Performance Report (Geosyntec Consultants & Wright

Water Engineers 2008) did not report EMC values specifically for SOGs, however the

database did contain information on these devices. Data from the following devices were

A-9

used to compute the EMC values summarized in Table A-6: Alameda, ARC Oil

Separator, Baffle Box, Baysaver 1, Boeing Oil/Water Separator, Environment 21 V2B1,

Stormceptor STC 3600, Urban Storm Treatment Unit in Madison, WI (Stormceptor),

Warr Oil and Grit Separator and Willis Drive Baffle Box.

Table A-6: Summary of sediment/oil/grease separator data obtained from the

International BMP Database


Median of Average

Outflow EMCs

Units






A.2.9. Inlet Inserts

Although values are reported for “media filters” in the Analysis of Treatment

Performance Report (Geosyntec Consultants & Wright Water Engineers 2008), the

analysis included some devices that are not inlet inserts (i.e. sand filters, media filter

vaults, etc.). In order to differentiate between types of media filters, EMC values

reported for BMPs under the categories “Geotextile Fabric Membrane (Vertical) Filter”

were sorted and analyzed separate from all other media filter BMPs. The names of those

BMPs in the database are: Rosemead SG, Las Flores SG, Foothill SG, Rosemead FF, Las

Flores FF and Footfill FF. The “SG” and “FF” in the names are presumed to stand for

A-10

“stream guard” and “fossil filter”, two types of propriety inlet insert devices. Table A-7

summarizes the data retrieved and computed average effluent value.

Table A-7: Summary of inlet insert data obtained from the International BMP

Database


Median of Average Outflow EMCs

Units






A.2.10. Porous Landscape Detention

Porous landscape detention (i.e. raingardens, bioretention, etc.) are categorized

under “Media Filters” and have a similar treatment mechanism as other media filters that

have a mixture of sand and some organic media. PLDs were lumped with other types of

similar media filters to determine EMC values for “media filter vaults”, therefore the

same EMC values are applied to PLDs in the model.

A.2.11. Retention Pond

The EMC values documented in the report for the category “Retention Ponds” are

used in the model.

A-11

A.2.12. Sand Filter Basin

The EMC values computed for “sand filter vaults” also are applied to sand filter

basins in the model.

A.2.13. Permeable Pavements

NOTE: This section added for BMP-REALCOST Version 1.0

The BMP database includes data from 14 permeable pavement installations, 7 of

which are classified as “permeable/porous asphalt” installations which are not included in

this model. Also, none of the 7 installations were classified as “porous gravel pavement”

(or similar) so no data were available for that PP type. Table A-8 lists the Test Site ID,

BMP ID, BMP Name, and classification of PP installation taken from the BMP Database

(V.2 – dated 12/19/2009).

Table A-8: Summary of PP installations with data available in the International

BMP Database

Test Site ID BMPID BMP Name Classification -1973863093 -2078844540 Austin Concrete Lot PCP 227406308 -1113891649 Austin Lattice Block Lot CGP 433547851 1366687752 Dayton Grass Pavement Parking Lot RGP 1079453569 -758940276 Porous Concrete Infiltration Basin PCP 1168373495 1615281267 Modular Block Porous Pavement PICP 1168980705 -2061314701 Cobblestone Porous Pavement PICP 1255059849 -1166835566 PICP PICP -1973863093 -2078844540 Austin Concrete Lot PCP 227406308 -1113891649 Austin Lattice Block Lot CGP 433547851 1366687752 Dayton Grass Pavement Parking Lot RGP Note: The classification was determined by the authors of this study for use in the BMP cost model and may differ from the classification listed in the BMP database due to classification aggregations.

A-12

Given the limited data available for all PP types as a whole, BMP effluent

statistics were computed from and applied to all PP installations aggregated together. In

other words, each PP type will have the same BMP effluent values, based on all data that

was available in the BMP database at the time. As more PP data in collected and input

into the BMP database, it is likely that the data may be disaggregated by BMP type to

better represent which PP types are more efficient than others. Table A-9 summarizes the

data retrieved and computed average effluent value.

Table A-9: Summary of permeable pavement data obtained from the International

BMP Database


Median of Average Outflow EMCs

Units






C. Methods, Sources and Assumptions Used to

Develop Maintenance Cost Estimates

C-2

C.1. Introduction

As with capital costs, it was preferred to develop cost equations that related annual

maintenance costs to the size of the BMP. Annual maintenance costs for a single BMP

typically reflect the costs of performing a wide variety of activities. Those activities can

generally be divided into two components; those with costs that vary according to the size

of the BMP (“variable” maintenance costs) and those that do not (“constant” maintenance

costs). The following equation was developed for estimating annual maintenance costs as

a function of multiple maintenance activities in both components.

BMPSizeAFAFMCostm

jjjj

n

iii ****

11

(C-1)

Where MCost = annual maintenance costs for an individual BMP, A = maintenance cost

for one unit of activity, F = frequency of maintenance per year, β= coefficient specifying

the number of maintenance units per unit of BMP size1, BMPSize = number of units of

BMP Size (AF, ft3, ft2, acre, cfs), i = indicates activities with “constant” maintenance

costs, j = indicates activities with “variable” maintenance costs, n = number of “constant”

maintenance activities for BMP and m = number of “variable” maintenance activities for

BMP.

Substituting a single variable for the summation terms, Equation (C-1) can be rewritten as

(C-2);

BMPSizeCvCcMCost * (C-2)

Where Cc = total annual cost for “constant” maintenance activities and Cv = total annual

unit cost for “variable” maintenance activities.

To use the equations above, it was necessary to determine the following information for

each BMP:

1 For example, if it is determined that approximately 1 acre of lawn needs mowing for every 3 acre-feet of

storage volume for RPs, then the coefficient value would be 0.33.

C-3

1. What typical maintenance activities are required or recommended?

2. How often does maintenance occur?

3. How much does one unit of maintenance cost?

4. What is the relationship (β-value) between unit maintenance costs and BMP

size for that activity?

C.2. Methodology

The methods, assumptions and data sources used to answer the four questions listed

above are described in this section.

C.2.1. Necessary Maintenance Activities

Published lists of recommended BMP maintenance activities are readily available. In

Chapter 3 of the Urban Storm Drainage Criteria Manual (USDCM) (UDFCD 2004),

UDFCD provides maintenance recommendations for many of the BMPs included in this

model. Other lists can be found on the EPA’s stormwater fact sheets

http://www.epa.gov/npdes/stormwater/menuofbmps).

Table C-1 lists the maintenance activities for each BMP included in the model.

Table C-1: Recommended maintenance activities

BMP Activity Frequency All Inspection 1

CGP Sweeping/Vacuuming 2 CWB Litter and Debris Removal 1 CWB Sediment Removal (forebay) 0.5 CWB Sediment Removal (basin) 0.05 CWC Litter and Debris Removal 1 CWC Vegetation/Woody Debris Removal 0.2 EDB Inlet/Outlet Cleaning 6 EDB Nuisance Control 12 EDB Outlet Maintenance 0.25 EDB Lawn Mowing/Lawn Care 6 EDB Sediment Removal (forebay/micropool) 0.5 EDB Sediment Removal (basin) 0.05 HS Sediment Removal 4 HS Traffic Control 4

C-4

BMP Activity Frequency II Sediment Removal 6

MFV Sediment Removal 2 PCP Sweeping/Vacuuming 2 PGP Gravel Finish Grading 12 PICP Sweeping/Vacuuming 2 PLD Annual Cleanup/Planting 1 RGB Lawn Mowing/Lawn Care 15 RP Nuisance Control 12 RP Lawn Mowing/Lawn Care 6 RP Sediment Removal (forebay/micropool) 0.5 RP Sediment Removal (basin) 0.05 RP Vegetation/Woody Debris Removal 0.33

SFB Lawn Mowing/Lawn Care 6 SFB Sediment Removal (forebay) 0.5 SFB Scarify Top Sand Layer 1 SFV Scarify Top Sand Layer 1 SOG Sediment Removal 4 SOG Traffic Control 4 VCV Sediment Removal 0.2

C.2.2. Frequency of Maintenance

The frequency of maintenance describes how often maintenance is performed (reported

in number of times per year) and varies according to the BMP for which it is being

performed. If the activity was only performed once every several years, than the value

would be less than 1. (For example: An activity performed once per five years would

have a value of 0.2 times per year.). The frequencies in Table C-1 were obtained from

interviews with stormwater maintenance personnel (Front Range Agencies 2008) and

from UDFCD recommendations in the USDCM (UDFCD, 2004).

C.2.3. Maintenance Activity Unit Costs

The maintenance activity unit costs are the costs to perform one unit of maintenance (for

example, the cost to remove 1 cubic foot of sediment from a BMP). These costs were

developed using “bottom-up” or “unit-pricing” cost estimating procedures. Equation

(C-3) is used to compute the maintenance unit cost for each activity.

2008$ OCECEOHLRLRCSEA **** (C-3)

C-5

Where A = maintenance unit cost, E = efficiency of maintenance, CS = labor crew size,

LR = hourly labor rate, OH = overhead factor, EC = equipment costs and OC = other

costs.

Annual O&M unit cost estimates were prepared using information collected during

interviews with seven stormwater utilities in the Denver, Colorado region, RSMeans

2005 Site Work & Landscape Cost Data Guide (RSMeans 2005) and vendor-provided

information. When sufficient cost information was provided from the stormwater utilities

it was used in the cost calculations. However, at times the utilities could not provide any

or all of the necessary information, so RS Means data was used to complement it.

C.2.4. Data Collection from Interviews with Stormwater Utilities

Personnel from seven stormwater utilities located near Denver, CO were interviewed to

gather information and costs on BMP maintenance. The interviewee(s) was asked to

estimate the average amount of resources (materials, equipment, personnel, etc.) and the

average frequency of maintenance required for its BMPs, based on proactive

maintenance2. In most cases, the interviewee(s) found it difficult to estimate “average”

values, particularly for frequency of maintenance and maintenance efficiency (number of

hours required), because they varied considerably from individual BMP to individual

BMP. Nevertheless, the interviewee(s) usually provided a “best guess” at the values.

Several utilities reported cost information for extended detention basins, hydrodynamic

separators and sediment/oil/grease separators; which are generally the most popular

BMPs used in the area. Only one utility could provide costs for a single sand filter vault

and porous concrete parking lot, another provided costs for a single constructed wetland

channel, and another provided “average” costs for retention ponds based on multiple

ponds located in its jurisdiction. The information collected during these interviews is

summarized in Table C-2 and Table C-3.

2 Keeping with project objectives which are to estimate the costs of proactive maintenance, not reactive.

C-6

C.2.5. Unit Cost Estimating Using RS Means

The RSMeans 2005 Site Work & Landscape Cost Data Guide (RSMeans 2005) was used

to complement the information gathered from the utility interviews. A summary of the

unit costs used from RS Means is provided in Table C-4 and Table C-5 All costs were

adjusted from 2005 dollars to 2008 dollars using the ENR CCI, and then regionally

adjusted to the Denver region using the RS Means region multiplier of 0.927.

C.2.6. Hourly Labor Rate

Average labor rates for stormwater maintenance personnel were collected from five

agencies located near Denver, Colorado (Table C-3). The average labor rate between

these was approximately $23.31 (in 2008 dollars).

C.2.7. Overhead Factor

It is assumed that overhead costs for maintenance personnel (insurance, vacation,

retirement contribution, etc.) is approximately equal to the hourly labor rate, therefore

this value is 100%.

C.2.8. Equipment Costs

Equipment costs are reported in Table C-3 and Table C-5 as hourly costs per piece of

equipment. Generally, when more than one reported cost existed for the same equipment,

the average of those costs was used in the model.

C.2.9. Other Costs

Other costs for materials, disposal, etc. are reported in Table C-3 and Table C-5 as unit

costs. Generally, when more than one unit cost was reported for the same item, the

average of those costs was used in the model.

C-7

Table C-2: Summary of maintenance activity information reported by Front Range Agencies

Activity Units Frequency Hours per Unit

Crew Equipment Other Costs Lump Sum Cost

Hydrodynamic Separator Sediment Removal CY 4 0.5 3 Jet-Vac Truck Sediment Disposal (wet) - Sediment Removal CY 4 2 2 Jet-Vac Truck Sediment Disposal (wet) - Sediment Removal CY 4 1.5 2 Jet-Vac Truck Sediment Disposal (wet) - Sediment Removal CY 4 4 2 Jet-Vac Truck Sediment Disposal (wet) - Sediment Removal CY 4 2 2 Jet-Vac Truck Sediment Disposal (wet) - Traffic Control (a) (a) (a) 3(b) Jet-Vac Truck - - Traffic Control (a) (a) (a) 3(b) Jet-Vac Truck - - Traffic Control (a) (a) (a) 1 Pick-up Truck - - Notes: – frequency and efficiency dependent on sediment removal – requires another street crew

Extended Detention Basin Inlet/Outlet Cleaning Each 6(c) 0.5 2 Pick-up Truck - - Inlet/Outlet Cleaning Each 6(c) 0.5 1 Pick-up Truck - - Inspection Each 6(c) 0.2 1 Pick-up Truck - - Inspection Each 6(c) 0.75 1 Pick-up Truck - - Lawn Mowing/Care Acre 3 2 2 Pick-up Truck

Tractor w/ Mower - -

Nuisance Control Each 24 0.8 1 Pick-up Truck - - Nuisance Control Each 12 0.25 2 Pick-up Truck - - Nuisance Control Each 10 0.5 1 Pick-up Truck Mosquito/Algae Tablets

($35) -

Outfall Maintenance (Rip-rap repair)

Each 0.2 12 3 Pick-up Truck (2) 3-CY Dumptrucks

Skidsteer

6 CY Rip-Rap(d) -

C-8



Outfall Maintenance (Rip-rap repair)

Each 0.33 - - - - $7,500

Sediment Removal (routine)

CY 0.5 0.33 2 Small Dumptruck Skidsteer

Sediment Disposal -

Sediment Removal (non-routine)

CY 0.1 0.08 4 Pick-up Truck Large Backhoe

(2) Large Dumptrucks

Sediment Disposal -

Notes: – after each major storm, assume 6 per year – assumed volume of riprap

Constructed Wetland Channel Debris and Litter Removal

Each 4 1.5 2 Pick-up Truck - -

Porous Concrete Outlet Cleaning Each 1 1 2 Jet-Vac Truck - -

Retention Pond Inspection Each 6(e) 0.2 1 Pick-up Truck - - Inspection Each 6(e) 0.75 1 Pick-up Truck - - Lawn Mowing/Care Acre 3 2 2 Pick-up Truck

Tractor w/ Mower - -

Tree Trimming Each 0.33 2 5 Pick-up Truck - - Nuisance Control Each 10 1 1 Pick-up Truck Mosquito/Algae Tablets

($70) -

Notes: – after each major storm, assume 6 per year

Sediment/Oil/Grease Separator Sediment Removal CY 4 1 3 Jet-Vac Truck Sediment Disposal (wet) - Sediment Removal CY 4 1.33 2 Jet-Vac Truck Sediment Disposal (wet) - Sediment Removal CY 12 - - - - $277

C-9



Traffic Control (f) (f) (f) 3(g) Jet-Vac Truck - - Traffic Control (f) (f) (f) 3(g) Jet-Vac Truck - - Traffic Control (f) (f) (f) 1 Pick-up Truck - -

Notes: – frequency and efficiency dependent on sediment removal – requires another street crew

Sand Filter Vault Remove Top Sand

Layer CY 1 1.6 2 Skidsteer

Dumptruck Sediment Disposal -

Table C-3: Summary of labor, equipment and materials costs reported by Front Range Agencies

Hourly Labor Rates Equipment Costs Other Costs Equipment Hourly Cost Material/Other Unit Cost

$20.33 Backhoe $46.01 Sediment Disposal $10/CY $21.24 Backhoe $62.00 Sediment Disposal $10/CY $24.00 Backhoe Trailer $9.99 Sediment Disposal $5/CY $26.00 Dumptruck

(tandem) $54.73 Sediment Disposal

(wet) $100/CY

$25.00 Flatbed Truck $10.02 Jet-Vac Truck $44.02 Jet-Vac Truck $83.00 Jet-Vac Truck $101.00 Jet-Vac Truck $200 Pick-up Truck $10.29 Pick-up Truck $10.00 Skidsteer $14.96

C-10

Table C-4: RS Means and Vendor-Provided Cost Information for Maintenance Activities

Activity Units Hours per Unit

Crew Equipment Other Costs

RS Means # / Vendor

Selective Clearing Acre 32 1 Pick-up Truck Brush Saw

- 02230-200-0020

Scarify Subsoil MSF 0.067 1 Skidsteer w/ Scarifier - 02910-710-3050 Site Maintenance, Hand Pick-up MSF 0.267 1 Pick-up Truck - 02985-700-1130 Flower Bed Maintenance, Spring Prepare MSF 4 1 Pick-up Truck - 02985-700-1200 Flower Bed Maintenance, Fall Clean-up MSF 8 1 Pick-up Truck - 02985-700-0830 Finish Grading, Large Area SY 0.008 2 Grader - 02310-100-0100

Vendor Provided Information for Inlet Insert Maintenance Inlet Filter Maintenance each 0.17 2 Pick-up Truck Debris

Disposal AbTech (2009) and ADS (2009)

Vendor Provided Information for Media Filter Vault Maintenance Sediment Removal CY 2 2 Jet-Vac Truck Sediment

Disposal Contech (2009)

Table C-5: RS Means Cost Information for Equipment and Materials

Equipment/Material Units Unit Cost RS Means # Dumptruck, Large (12-ton) Hr $55.18 01590-200-5250 Skidsteer, 1 CY Hr $34.81 01590-200-4890 Tractor w/ Rotary Mower Hr $28.99 02230-200-1080 Excavator, 1 CY Hr $99.68 01590-200-0150 Dumptruck, Small (1.5-ton) Hr $19.18 01590-200-5450 Brush Saw Hr $2.44 Crew Description A-1C Street Sweeper Hr $78.29 01500-500-3400 Grader Hr $31.81 Crew Description B-11L Rip-Rap (18” thickness) SY $15.79 02370-450-200

C-11

C.2.10. Efficiency of Maintenance

The efficiency of maintenance variable accounts for how much time each maintenance

activity requires. More specifically, the actual value represents the number of hours

required to complete one unit of maintenance. For example, if it requires approximately

30 minutes to mow 1 acre of grass, then E = 0.5. Generally, when more than one

efficiency value was reported for the same activity, the average of those costs was used in

the model.

C.2.11. Labor Crew Size

The labor crew size is the number of maintenance personnel needed to complete the

maintenance activity. Generally, when more than crew size was reported for the same

activity, the average of those values was used in the model.

C.2.12. Summary

Table C-6 shows the computed maintenance unit costs for each activity, alongside the

estimated values of each variable as presented in the preceding sections.

C-12

Table C-6: Summary of Maintenance Unit Costs Developed for the UDFCD BMP Effectiveness and Cost Analysis Model

Activity Units Hours

per UnitCrew Size

Equipment Required Equipment

Cost/hr1 Other

Materials Other Costs

Cost per Unit2

Inspection Each 0.33 1 Pickup Truck $10.15 - - $19 Inlet/Outlet

Cleaning Each 0.5 2 Pickup Truck $10.15 - - $52

Nuisance Control (EDB)

Each 0.5 1 Pickup Truck $10.15 Product $35 $63

Nuisance Control (RP)

Each 1 1 Pickup Truck $10.15 Product $70 $127

Outfall Maintenance Each 12 3 Pickup Truck

Large Dumptruck Skidsteer

$10.15 $55.18 $37.55

Rip-Rap $2003 $3,113

Lawn Mowing/Lawn Care

Acre 2 2 Pickup Truck

Tractor w/ Rotary Mower $10.15 $31.27

- - $269

Sediment Removal – Non-Routine4

CY 0.08 4 Pickup Truck

Large Excavator 2 Large Dumptrucks

$10.15 $99.68 $110.36

Sediment Disposal

$10 $43

Sediment Removal – Routine5

CY 0.33 2 Small Dumptruck

Skidsteer $19.18 $37.55

Sediment Disposal

$10 $59

Sediment Removal 6 CY 1.2 2 Jet-Vac Truck $110 Sediment Disposal

$100 $344

Sediment Removal7 CY 2 2 Jet-Vac Truck $110 Sediment Disposal

$100 $558

Traffic Control8 CY 1.2 2 Pickup Truck $10.15 - - $124 Traffic Control8 CY 2 2 Pickup Truck $10.15 - - $277

Vegetation/Woody Debris Removal

Acre 16 2 Pickup Truck

Brush Saw $10.15 $2.62

- - $1,696

Scarify Top Sand Layer (SFB)

Acre 3 1 Skidsteer w/ Scarifiers $37.55 - - $253

C-13

Activity Units Hours

per UnitCrew Size

Equipment Required Equipment

Cost/hr1 Other

Materials Other Costs

Cost per Unit2

Remove Top Sand Layer (SFV)9

CY 2 2 Skidsteer

Small Dumptruck $37.55 $19.18

Sand Disposal

$10 $310

Litter & Debris Removal

Acre 6 2 Pickup Truck $10.15 - - $620

Annual Cleanup MSF 4 2 Pickup Truck $10.15 - - $414 Annual Planting MSF 2 2 Pickup Truck $10.15 - - $207

Finish Grading Acre 6 1 Grader $31.81 - - $471

Pavement Sweeping Acre 0.5 1 Street Sweeper/Vacuum $78.29 - - $62

Inlet Filter Maintenance

Each 0.17 2 Pick-up Truck $10.15 Debris

Disposal $10 $165

1 Unless otherwise noted, hourly equipment costs include rental and operating costs, as reported in RSMeans 2005. 2 Assumes labor rate of $23.31 per hour and overhead costs equal to 100% of labor rate 3 Assumes approximately 6 CY of rip-rap 4 Applicable to large basin facilities such as extended detention basins, retention (wet) ponds, and constructed wetland basins 5 Sediment removal from forebay for large basin facilities 6 Applicable to hydrodynamic separators and sediment/oil/grease separators. 7 Applicable to media filter vaults 8 Required for sediment removal from underground structures, therefore the efforts are a function of the amount of sediment needing removal 9 Costs apply for “Delaware-type” filters where access to the filter is available by removing inlet grates, allowing access for equipment

C-14

C.3. BMP Size/Unit Maintenance Cost Relationship (β-value)

Relationships between BMP size and unit maintenance costs were determined using BMP

design recommendation and other assumptions. The reported β-value represents the

number of maintenance units per unit of BMP size plus the appropriate unit conversions.

C.3.1. Concrete Grip Pavers

Pavement Sweeping/Vacuuming – Pavement sweeping and/or vacuuming occurs over the

entire surface area of the installation. The β-value = 1

Sweeping/Vacuuming (acres) = Surface Area (acres) * 1(acre/acre) (C-4)

C.3.2. Constructed Wetland Basin

Sediment Removal (routine) – Routine sediment removal is assumed to be performed

when the basin forebay has reached its sediment holding capacity (20% of the total

forebay volume). The basin forebay volume should be about 10% of the total pond

volume, therefore the amount of sediment removed from the forebay is equal to 2% of the

total basin volume. The β-value = 32.27, including the unit conversion from AF to CY.

Sediment Removed (CY) = Volume (AF) * 32.27 (CY/AF) (C-5)

Sediment Removal (non-routine) – Non-routine sediment removal is assumed to be

performed when 20% of the storage volume has accumulated sediment. The β-value =

322.67, including the unit conversion from AF to CY.

Sediment Removed (CY) = Volume (AF) * 322.67(CY/AF) (C-6)

Litter and Debris – The area requiring litter and debris removal is assumed to 50% of the

total area consumed by the basin. Assuming 1 acre of land consumed per AF of storage

volume, the β-value = 0.5

Litter and Debris Removal (acre) = Volume (AF) * 0.5 (acres/AF) (C-7)

C-15

C.3.3. Constructed Wetland Channel

The size of CWCs are reported as the design flowrate (cfs), however maintenance costs

are computed as a function of the surface area of the channel.

Vegetation/Woody Debris Removal – The area requiring vegetation and woody debris

removal is assumed to be the total area consumed by the channel. The β-value = 1

Vegetation/Woody Debris Removal (acre) = Area of Channel (acre) * 1(acres/acres)

(C-8)

Litter and Debris – The area requiring litter and debris removal is assumed to be the total

area consumed by the channel. The β-value = 1

Litter and Debris Removal (acre) = Area of Channel (acre) * 1(acres/acres) (C-9)

C.3.4. Extended Detention Basin


when the EDB forebay has reached its sediment holding capacity (20% of the total

forebay volume). The EDB forebay volume should be about 5% of the total EDB


total EDB volume. The β-value = 16.13, including the unit conversion from AF to CY.



performed when the EDB has reached its sediment holding capacity (20% of total EDB

volume). The β-value = 322.67, including the unit conversion from AF to CY.

Sediment Removed (CY) = Volume (AF) * 322.67 (CY/AF) (C-11)

Lawn Care/Lawn Mowing – Lawn care/mowing is assumed to be required over the entire

area consumed by the EDB. Assuming 1 acre of land required per AF of storage volume,

the β-value = 1.

C-16

Lawn Care/Lawn Mowing (acre) = Volume (AF) * 1 (acre/AF) (C-12)

C.3.5. Hydrodynamic Separator

Sediment Removal – Sediment removal is assumed to be performed when the sediment

holding capacity of the system is full. Each proprietary system has a unique relationship

between sediment holding capacity and design flowrate, therefore a regression equation

was developed using the relationships from three systems with information readily

available3. The relationships and regression equation are presented in Figure C-1.

y = 0.4028x

R2 = 0.7035

0

2

4

6

8

10

12

0 5 10 15 20 25 30

Treatment Flow Rate (cfs)

Sed

imen

t S

tora

ge

(CY

)

Figure C-1: Sediment storage and design flowrate relationships for hydrodynamic

separators

3 The systems used to establish the relationship were the Downstream Defender, Aqua-Swirl, and Vortechs;

using information provided in product brochures.

C-17

The β-value for sediment removal in hydrodynamic separators is 0.4

Sediment Removed (CY) = Design Flowrate (cfs) * 0.4 (CY/cfs) (C-13)

Traffic Control – Traffic control is assumed to be required during sediment removal

maintenance, therefore the same relationship described for sediment removal applies for

traffic control. The β-value = 0.4

C.3.6. Media Filter Vault


holding capacity of the system is full. Information available from two proprietary media

filter systems suggest an average sediment holding capacity of 18 ft3 (0.67 CY) per cfs of

design flow.

Sediment Removal (CY) = Flowrate (cfs) * 0.67 (CY/cfs) (C-14)




C.3.7. Permeable Interlocking Concrete Pavers




C.3.8. Porous Concrete Pavement




C-18

C.3.9. Porous Gravel Pavement

Gravel Finish Grading - Grading occurs over the entire surface area of the installation.

The β-value = 1

Gravel Grading (acres) = Surface Area (acres) * 1(acre/acre) (C-17)

C.3.10. Porous Landscape Detention

Annual Cleanup/Planting – The area requiring cleanup and planting is assumed to be the

total surface area consumed by the BMP, which is the same as the storage volume of the

PLD when assuming that water can pond up to 1 foot on top of the PLD. The β-value =

0.001.

Cleanup and Planting (MSF) = Volume(CF) * 0.001(MSF/CF) (C-18)

C.3.11. Reinforced Grass Pavement

Lawn Care/Lawn Mowing – Lawn care/mowing is assumed to be required over the entire

surface area of the installation (β-value = 1).

Lawn Care/Lawn Mowing (acre) = Surface Area (acres)) * 1(acre/acre) (C-19)

C.3.12. Retention (Wet) Pond

Lawn Care/Lawn Mowing – Lawn care/mowing is assumed to be required over 50% of

the area consumed by the BMP. Assuming 0.5 acres of land required per AF of storage

volume, the β-value = 0.25.

Lawn Care/Lawn Mowing (acre) = Volume (AF) * 0.25(acres/AF) (C-20)


when the pond forebay has reached its sediment holding capacity (20% of the total

forebay volume). The pond forebay volume should be about 5% of the total pond


total pond volume. The β-value = 16.13.

C-19



performed when the pond has reached its sediment holding capacity (20% of total pond

volume). The β-value = 322.67


Vegetation/Woody Debris Removal – The area requiring vegetation and woody debris

removal is assumed to 10% of the total area consumed by the pond. Assuming 0.5 acres

of land required per 1 AF of storage volume, the β-value = 0.05.

Vegetation/Woody Debris Removal (acre) = Volume (AF) * 0.05(acres/AF)

(C-23)

C.3.13. Sand Filter Basin

Lawn Care/Lawn Mowing – Lawn care/mowing is assumed to be required over 50% of

the area consumed by the BMP. Assuming that 1 acre of land is required per 1.5 AF of

storage volume, the β-value = 0.33.

Lawn Care/Lawn Mowing (acre) = Volume (AF) * 0.33 (acres/AF) (C-24)


when the basin forebay has reached its sediment holding capacity (20% of the total

forebay volume). The forebay volume should be about 5% of the total basin volume,

therefore the amount of sediment removed from the forebay is equal to 1% of the total

pond volume. The β-value = 16.13.


Scarify Top Sand Layer – Scarifying is required over the entire surface area of the sand

filter, which is 1 ft2 per CF of storage volume. The β-value = 0.33.

C-20

Scarifying Area (acre) = Volume (AF) * 0.33 (acres/AF) (C-26)

C.3.14. Sand Filter Vault

Remove top media layer – Assuming that the top two inches are removed from the

surface area of the vault, the surface area is approximately 33% of the total volume of

media (i.e. the SFV is three feet deep), and the total volume of media is approximately

300% of the total volume of water storage (33% pore openings in media), the β-value =

0.006 including the unit conversion from CF to CY.

Top Sand Layer (CY) = Volume (CF) *0.006(CY/CF) (C-27)

C.3.15. Sediment/Oil/Grease Separator


holding capacity of the system is full. Each proprietary system has a unique relationship

between sediment holding capacity and design flowrate, therefore a regression equation

was developed using the relationships from three systems with information readily

available4. The relationships and regression equation are presented in Figure C-2.

4 The systems used to establish the relationship were the VortClarex, Stormceptor, Baysaver and V2B1;

using information provided in product brochures.

C-21

y = 0.4389x

R2 = 0.7487

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0.00 5.00 10.00 15.00 20.00 25.00

Treatment Flow Rate (cfs)

Sed

imen

t S

tora

ge

(CY

)

Figure C-2: Sediment storage and design flowrate relationships for

sediment/oil/grease separators

The β-value for sediment removal in sediment/oil/grease separators is 0.44

Sediment Removed (CY) = Design Flowrate (cfs) * 0.44(CY/cfs) (C-28)




C.3.16. Vault with Capture Volume


when the vault has reached its sediment holding capacity (20% of the total volume). The

β-value = 0.007 including the unit conversion from CF to CY.

Sediment Removed (CY) = Volume (CF) * 0.007 (CY/CF) (C-29)

C-22

C.4. Maintenance Cost Equations

The maintenance cost equations developed for each BMP are described below. It should

be noted that these cost equations are set as “default” values in the model, however the

maintenance cost tables are user-editable and can be changed to fit any known

maintenance costs.

C.4.1. Compliance Inspection

One activity that is common to all BMPs is inspection and the maintenance tables for

each BMP include inspections. However in the model, inspections are considered

administrative activities, not maintenance activities, therefore the costs of performing

inspections are added to the annual administrative costs instead of the annual

maintenance costs.

C.4.2. Concrete Grid/ Permeable Interlocking Concrete Block Pavers

Table C-7 summarizes the maintenance activities and their individual annual costs for

cobblestone and modular block pavement. Equation (C-30) is used to compute total

annual maintenance costs.

Table C-7: CGP/PICP maintenance activity costs

Activity Type Freq A β-value Annual Cost* - - - - - -

Total = - Sweeping/Vacuuming Variable 2 $62 1 $125

Total = $125 Notes:

* – for unit-type activities, the annual cost is per acre of installation surface area

2008$ )(*125$ acresBMPSizeMCost (C-30)

C-23

C.4.3. Constructed Wetland Basin


CWBs. Equation (C-31) is used to compute total annual maintenance costs.

Table C-8: CWB maintenance activity costs

Activity Type Freq A β-value Annual Cost* - - - - - -

Total = - Litter and Debris Removal Unit 1 $620 0.5 $310 Sediment Removal (routine)

Unit 0.5 $60 32.27 $960


Unit 0.05 $43 322.67 $686

Total = $1,956 Notes:

* – for unit-type activities, the annual cost is per AF of storage volume

2008$ )(*956,1$ AFBMPSizeMCost (C-31)

C.4.4. Constructed Wetland Channel


CWCs. Equation (C-32) is used to compute total annual maintenance costs.

Table C-9: CWC maintenance activity costs

Activity Type F A β-value Annual Cost* - - - - - -

Total = - Litter and Debris Removal Unit 1 $620 1 $620 Vegetation/Woody Debris Removal

Unit 0.2 $1,969 1 $339

Total = $960 Notes:

* – for unit-type activities, the annual cost is per acre of surface area

C-24


C.4.5. Extended Detention Basin


EDBs. Equation (C-33) is used to compute total annual maintenance costs for EDBs.

Table C-10: EDB maintenance activity costs

Activity Type F A β-value Annual Cost* Inlet/Outlet Cleaning Lump sum 6 $52 - $310 Nuisance Control Lump sum 12 $63 - $761 Outlet Maintenance Lump sum 0.25 $3,113 - $778

Total = $1,849 Lawn Mowing/Lawn Care Unit 6 $269 1 $2,151 Sediment Removal (routine)

Unit 0.5 $60 16.13 $480


Unit 0.05 $43 322.67 $686


* – for unit-type activities, the annual cost is per AF of EDB storage

2008$ )(*782,2$849,1$ AFBMPSizeMCost (C-33)

C.4.6. Hydrodynamic Separator


EDBs. Equation (C-34) is used to compute total annual maintenance costs.

Table C-11: HS maintenance activity costs


Total = - Sediment Removal Unit 4 $344 0.4 $550 Traffic Control Unit 4 $124 0.4 $199

Total = $749

C-25

Notes:

* – for unit-type activities, the annual cost is per cfs of design flowrate

2008$ )(*749$ cfsBMPSizeMCost (C-34)

C.4.7. Inlet Inserts



Table C-12: II maintenance activity costs

Activity Type F A β-value Annual Cost Filter Replacement Lump sum 6 $166 - $166

Total = $166 - - - - - -

Total = - Notes:

2008$ 166$MCost (C-35)

C.4.8. Media Filter Vault



Table C-13: MFV maintenance activity costs



Total = $835 Notes:

* – for unit-type activities, the annual cost is per cfs of design flowrate

C-26


C.4.9. Porous Concrete Pavement



Table C-14: PCP maintenance activity costs


Total = - Sweeping/Vacuuming Unit 2 $62 1 $125

Total = $125 Notes:

* – for unit-type activities, the annual cost is per acre of installation surface area.


C.4.10. Porous Gravel Pavement



Table C-15: PGP maintenance activity costs


Total = - Gravel Finish Grading Unit 12 $471 1 $5,647


* – for unit-type activities, the annual cost is per acre of installation surface area.

2008$ BMPSizeMCost *647,5$ (C-38)

C-27

C.4.11. Porous Landscape Detention



Table C-16: PLD maintenance activity costs


Total = - Annual Cleanup Unit 1 $414 0.001 $0.41 Annual Planting Unit 1 $207 0.001 $0.21

Total = $0.62 Notes:

* – for unit-type activities, the annual cost is per CF of storage volume

2008$ )(*62.0$ CFBMPSizeMCost (C-39)

C.4.12. Reinforced Grass Pavement



Table C-17: RGP maintenance activity costs


Total = - Lawn Mowing/Lawn Care Unit 15 $269 1 $4,040


* – for unit-type activities, the annual cost is per acre of installation surface area

2008$ )(*040,4$ acresBMPSizeMCost (C-40)

C-28

C.4.13. Retention Pond



Table C-18: RP maintenance activity costs

Activity Type F A β-value Annual Cost* Nuisance Control Lump sum 12 $127 - $1,521

Total = $1,521 Lawn Mowing/Lawn Care Unit 6 $269 1 $404 Sediment Removal (routine)

Unit 0.5 $60 16.13 $480


Unit 0.05 $43 322.67 $686

Vegetation/Woody Debris Removal

Unit 0.33 $1,696 0.05 $28



2008$ )(*598,1$521,1$ AFBMPSizeMCost (C-41)

C.4.14. Sand Filter Basin



Table C-19: SFB maintenance activity costs


Total = - Lawn Mowing/Lawn Care Unit 6 $269 0.33 $533 Sediment Removal (routine)

Unit 0.5 $60 16.13 $480

Scarify Top Sand Layer Unit 1 $253 0.33 $83 Total = $1,096

Notes:

C-29


2008$ )(*096,1$ AFBMPSizeMCost (C-42)

C.4.15. Sand Filter Vault



Table C-20: SFV maintenance activity costs


Total = - Remove Top Sand Layer Unit 1 $310 0.006 $1.86




C.4.16. Sediment/Oil/Grease Separator



Table C-21: SOG maintenance activity costs



Total = $832 Notes:

* – for unit-type activities, the annual cost is per cfs of design flowrate.

C-30


C.4.17. Vault with Capture Volume


VCVs. Equation (C-45) is used to compute total annual maintenance costs.

Table C-22: VCV maintenance activity costs


Total = - Sediment Removal Unit 0.2 $344 0.007 $0.48 Traffic Control Unit 0.2 $129 0.007 $0.18




B. Permanent BMP Construction Cost Estimates

Muller Engineering Company, Inc. Consulting Engineers Irongate 4, Suite 100 777 South Wadsworth Blvd. Lakewood, Colorado 80226 (303) 988-4939 Memorandum

Permanent BMP Construction Cost Estimates To: Ken MacKenzie / UDFCD Holly Piza / UDFCD

From: Melanie Chenard / Muller Engineering Company

Jim Wulliman / Muller Engineering Company Bruce Behrer / Muller Engineering Company

Date: August 3, 2009 Muller Engineering Company has prepared order-of-magnitude opinions of probable construction cost for a variety of permanent stormwater best management practices (BMPs). Each BMP was sized for the water quality capture volume (WQCV) per UDFCD criteria, excess urban runoff volume (EURV), an estimated water quality flow rate, or other sizing criteria, as applicable. Each BMP was sized for three different contributing impervious areas, ranging from 0.25 ac to 20 ac. The BMPs were organized into several categories, each with their own basis of sizing, as shown in Table 1. Table 1. Types of BMPs and Basis of Sizing

Type of BMP Basis of Sizing Number of BMPs Evaluated

WQCV BMPs

WQCV, per criteria 8

Porous Pavement BMPs

One-half of upstream impervious area

5

Proprietary BMPs

Water quality event peak discharge

4

Channel BMPs

2-year / 100-year peak discharge

1

EURV BMPs EURV, per criteria 3

Table 2, on the next page, lists all of the BMPs evaluated and the basis of their sizing. Sizing calculations are shown in Appendix A. Summary charts showing construction cost opinions for all of the BMPs are provided in Appendix B. Spreadsheets showing design assumptions, quantity estimates, unit costs and total costs, along with any plan or section drawings of BMPs are provided in Appendices C, D, E, and F, respectively, for WQCV BMPs, porous pavement BMPs, proprietary BMPs, and channel BMPs.

Memorandum August 3, 2009 Page 2 Quantities were estimated based on BMP configurations shown in Volume 3 of the Urban Storm Drainage Criteria Manual (USDCM), where available, and construction unit costs were applied based on recent bids received/reviewed by Muller, CDOT 2008 Cost Data, UDFCD Bid Tabulation Data, and manufacturer-provided data. Past project cost data originated from recent projects constructed in the past 5 years within the Denver metropolitan area and so adjustments for inflation and geographic location were not made. Table 2. BMPs Evaluated and Their Relative Size

Impervious area, ac 0.25 1 2 5 20

WQCV BMPs Water Quality Capture Volume, AF 1 Extended Detention Basin (EDB) 0.10 0.25 1.00 2 Constructed Wetland Basin (CWB) 0.08 0.19 0.75 3 Retention Pond (RP) 0.07 0.17 0.67 4 Sand Filter Basin (SFB) 0.04 0.08 0.21

5 Porous Landscape Detention (PLD) with media walls 0.01 0.03 0.17

6 Porous Landscape Detention (PLD) without media walls 0.01 0.03 0.17

7 Underground Vault with WQCV 0.01 0.04 0.10 8 Underground Sand Filter Vault 0.01 0.04 0.08

Porous pavement BMPs Area, ac 9 Modular Block Pavement (MBP) 0.08 0.33 0.66 10 Cobblestone Block Pavement (CBP) 0.08 0.33 0.66 11 Reinforced Grass Pavement (RGP) 0.08 0.33 0.66 12 Porous Concrete Pavement (PCP) 0.08 0.33 0.66 13 Porous Gravel Pavement (PGP) 0.08 0.33 0.66

Proprietary BMPs Water Quality Event Peak Discharge, cfs 14 Hydrodynamic Separators 0.3 1.1 2.1 15 Oil/grease/sediment Separators 0.3 1.1 2.1 16 Media Filters 0.3 1.1 2.1 17 Inlet Filters 0.3 1.1 2.1

Channel BMPs 2‐year Peak Discharge, cfs 18 Constructed Wetland Channel (CWC) 4.1 10 32

EURV BMPs Excess Urban Runoff Volume, AF 1 Extended Detention Basin (EDB) 0.20 0.51 2.02 2 Constructed Wetland Basin (CWB) 0.20 0.51 2.02 3 Retention Pond (RP) 0.20 0.51 2.02

Memorandum August 3, 2009 Page 3

The order-of-magnitude opinions of probable construction cost presented herein are approximate and intended primarily for comparative purposes. Design configurations were simplified and assumptions were made in an effort to represent the cost of an “average” installation of each BMP; however, varying site conditions can have tremendous impact on the actual cost of any BMP and the costs shown herein are not intended to be absolute. The costs of manufactured products can be especially sensitive to design assumptions and specific site conditions. Because of the uncertainty associated with proprietary BMP design approaches, effectiveness, and costs, we have shown these construction cost opinions as possible ranges for each type of proprietary BMP rather than plotting costs associated with any one manufacturer’s product. The BMPs examined do not necessarily have the same treatment effectiveness, even if they are sized for similar contributing impervious areas. Therefore, comparing costs of the BMPs for the same impervious area does not in itself reveal the relative treatment costs per pound of pollutant removed. We have appreciated the opportunity to work with you on this evaluation of BMP cost information and look forward to further discussions with you.

Appendix A

BMP Sizing Calculations

UDFCD BMP Construction Cost Evaluation7/31/2009

Drainage AreaContributing area, ac 0.25 1 2 5 20% imperviousness 100% 100% 100% 100% 100%Impervious area, ac 0.25 1 2 5 20

Rational Method FlowsAsssumed width of contributing area, ft 60 120 165 260 500Length of contributing area, ft 182 363 528 838 1742L/W 3.0 3.0 3.2 3.2 3.5Tc 11 12 13 15 20100‐year rainfall intensity 6.8 6.6 6.3 5.9 5.1100‐year C 0.96 0.96 0.96 0.96 0.96100‐year peak flow 1.6 6.3 12 28 98

2‐year rainfall intensity 2.5 2.4 2.3 2.2 1.82‐year C 0.89 0.89 0.89 0.89 0.892‐year peak flow 0.6 2.1 4.1 10 32

WQ event rainfall intensity 1.3 1.3 1.2 1.2 0.9WQ event C 0.88 0.88 0.88 0.88 0.88WQ event peak flow 0.3 1.1 2.1 5.1 16.7

WQCVPorous pavementsRatio of porous to total impervious area 0.33 0.33 0.33 0.33 0.33Porous area, ac 0.08 0.33 0.66 1.65 6.6

Extended Detention Basin (EDB)Drain time, hrs 40a 1 1 1 1 1Additional volume for sediment storage 20% 20% 20% 20% 20%WQCV, in 0.5 0.5 0.5 0.5 0.5WQCV with sediment storage, in 0.6 0.6 0.6 0.6 0.6WQCV with sediment storage, CF 545 2178 4356 10890 43560WQCV with sediment storage, AF 0.01 0.05 0.10 0.25 1.00

Sand Filter Basin (SFB)Drain time, hrs 40a 1 1 1 1 1WQCV, in 0.5 0.5 0.5 0.5 0.5WQCV, CF 454 1815 3630 9075 36300WQCV, AF 0.01 0.04 0.08 0.21 0.83

Constructed Wetland Basin (CWB)Drain time, hrs 24a 0.9 0.9 0.9 0.9 0.9Additional volume for sediment storage 0% 0% 0% 0% 0%WQCV, in 0.45 0.45 0.45 0.45 0.45WQCV, CF 408 1634 3267 8168 32670WQCV, AF 0.01 0.04 0.08 0.19 0.75

Retention Pond (RP)Drain time, hrs 12a 0.8 0.8 0.8 0.8 0.8Additional volume for sediment storage 0% 0% 0% 0% 0%WQCV, in 0.4 0.4 0.4 0.4 0.4WQCV, CF 363 1452 2904 7260 29040WQCV, AF 0.01 0.03 0.07 0.17 0.67

Porous Landscape Detention (PLD)Drain time, hrs 12a 0.8 0.8 0.8 0.8 0.8Additional volume for sediment storage 0% 0% 0% 0% 0%WQCV, in 0.4 0.4 0.4 0.4 0.4WQCV, CF 363 1452 2904 7260 29040WQCV, AF 0.01 0.03 0.07 0.17 0.67Max WQCV depth, in 12 12 12 12 12Min area, ac 0.01 0.03 0.07 0.17 0.67

EURVEURV, in 1.21 1.21 1.21 1.21 1.21EURV, CF 1102 4409 8818 22045 88181EURV, AF 0.03 0.10 0.20 0.51 2.02Max release rate, cfs 0.25 1 2 5 20

Appendix B

Summary Charts Showing Order-of-Magnitude Opinions of Probable Construction Cost

$80,000

$100,000

$120,000

nstruction

Cost

Opinion of Probable Construction Costs for WQCV BMPs

SFB VAULT

WQCV VAULT

PLD (With Media Walls)

PLD (Without Media Walls)

RP

SFB

CWB

EDB

$0

$20,000

$40,000

$60,000

0 2 4 6 8 10 12 14 16 18 20

Opinion

of P

roba

ble Co

n

Contributing Impervious Area (ac)

$250,000

$300,000

$350,000

$400,000

onstruction Co

stOpinion of Probable Construction Cost

for Porous Pavement BMPs

CBP

PCP

MBP

RGP

PGP

$0

$50,000

$100,000

$150,000

$200,000

0 0.5 1 1.5 2 2.5

Opinion

of P

roba

ble Co


$150,000

$200,000

$250,000 Con

struction Co

st

Opinion of Probable Construction Costs for Proprietary BMPs

Media Filter Cost Opinion (High)

Media Filter Cost Opinion (Low)

Hydrodynamic Devices/Oil Separators Cost Opinion (High)

Hydrodynamic Devices/Oil Separators (Low)

Inlet Filters Cost Opinion (High)

Inlet Filters Cost Opinion (Low)

$0

$50,000

$100,000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Opinion

of P

roba

ble


$5,000

$6,000

$7,000

$8,000 Con

struction

00 LF

Opinion of Probable Construction Costfor Constructed Wetland Channel

$0

$1,000

$2,000

$3,000

$4,000

0 5 10 15 20 25

Opinion

of P

roba

ble

Cost per 10


$40,000

$50,000

$60,000

$70,000

nstruction

Cost

Opinion of Probable Construction Costs for EURV BMPs

$0

$10,000

$20,000

$30,000

$ ,

0 2 4 6 8 10 12 14 16 18 20

Opinion

of P

roba

ble Co

n


CWB (EURV)

EDB (EURV)

RP (EURV)

Appendix C

Cost Spreadsheets and Figures for WQCV BMPs

Extended Detention Basin (EDB) with WQCV

Design Information

WQCV depth range 2-4 ftForebay depth 2 ftForebay volume (% of WQCV) 4%Basin length:width ratio 3Side slopes (H:V) 5Maintenance road width 10 ftMaintenance road slope 0.10 ft/ftMaintenance road thickness 1.0 ft

WQCV (incl. sediment storage) 4356 cf 10890 cf 43560 cfWQCV depth 2 ft 2 ft 4 ft100-yr peak flow 12 cfs 28 cfs 98 cfsWQ event peak flow 2.1 cfs 5.1 cfs 16.7 cfs used for calculating pipe size assuming 1% slopeForebay volume 174 cf 436 cf 1742 cfForebay area 87 sf 218 sf 871 sfArea at 1/2 WQCV depth 2178 sf 5445 sf 10890 sfWidth at 1/2 WQCV depth 27 ft 43 ft 60 ftLength at 1/2 WQCV depth 81 ft 128 ft 181 ftTop area 3356 sf 7249 sf 16110 sfBottom area 1200 sf 3841 sf 6470 sfEmergency spillway width (assume 1' head) 4 ft 9 ft 33 ftMaintenance road length 121 ft 168 ft 261 ftTrickle channel width 2 ft 2 ft 4 ftTrickle channel length 54 ft 85 ft 120 ft

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total Notes1 Excavation and backfill CY $5 161 $807 403 $2,017 807 $4,033 100% WQCV for 2 & 5 acre sites, 50% WQCV for 20 acre site2 Concrete forebay CY $400 2 $800 5 $2,000 17 $6,800 qty based on area*2 for sides, ramps, etc.3 Outlet structure - 2.1 and 5.1 cfs capacity LS $10,000 1 $10,000 1 $10,000 0 $04 Outlet structure - 17 cfs capacity LS $15,000 0 $0 0 $0 1 $15,0005 Riprap spillway protection CY $60 5 $300 12 $720 44 $2,640 1.5' thickness; 4:1 slope6 Concrete spillway weir CY $400 0.3 $120 0.4 $160 0.9 $3607 Maintenance access road (aggregate base course) CY $40 45 $1,800 62 $2,480 97 $3,880 basin length + 2 bottom accesses8 Upland seeding and mulching AC $2,000 0.10 $200 0.20 $400 0.45 $900 120% of top area9 18" RCP LF $50 50 $2,500 50 $2,500 0 $0

10 24" RCP LF $55 0 $0 0 $0 50 $2,75011 Concrete trickle channel CY $400 4 $1,600 6 $2,400 13 $5,200 2/3 basin length, 6" thick, 4" deep

SUBTOTAL $18,127 $22,677 $41,563Mobilization and site prep 7% $1,269 $1,587 $2,909TOTAL COST $19,396 $24,264 $44,473

20 Acre Site

Contributing Impervious Area2 ac 5 ac 20 ac

2 Acre Site 5 Acre Site

P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsEDB 8/3/2009

Constructed Wetlands Basin (CWB) with WQCV

Design Information

WQCV depth 2 ftForebay depth (below permanent pool) 3 ftPermanent pool volume (% of WQCV) 75%Forebay volume (% of WQCV) 8%Basin length:width ratio 3Side slopes (H:V) 5Maintenance road width 10 ftMaintenance road slope 0.10 ft/ftMaintenance road thickness 1.0 ftWetland vegetation area (% of permanent pool) 60%

WQCV 3267 cf 8168 cf 32670 cf100-yr peak flow 12 cfs 28 cfs 98 cfsWQ event peak flow 2.1 cfs 5.1 cfs 16.7 cfs used for calculating pipe size assuming 1% slopePermanent pool volume 2450 cf 6126 cf 24503 cfForebay volume 261 cf 653 cf 2614 cfForebay area 87 sf 218 sf 871 sfArea at 1/2 WQCV depth 1634 sf 4084 sf 16335 sfWidth at 1/2 WQCV depth 23 ft 37 ft 74 ftLength at 1/2 WQCV depth 70 ft 111 ft 221 ftTop area 2667 sf 5660 sf 19387 sfPermanent pool area 800 sf 2708 sf 13483 sfAverage permanent pool depth 3.1 ft 2.3 ft 1.8 ftEmergency spillway width (assume 1' head) 4 ft 9 ft 33 ftMaintenance road length 110 ft 151 ft 261 ft

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total Notes

1 Excavation and backfill CY $5 212 $1,059 529 $2,647 1513 $7,563Permanent pool plus: 100% WQCV for 2 & 5 acre sites, 50% WQCV for 20 acre site

2 Concrete forebay CY $400 4 $1,600 9 $3,600 33 $13,200 qty based on area*2 for sides, ramps, etc.3 Outlet structure - 2.1 and 5.1 cfs capacity LS $10,000 1 $10,000 1 $10,000 0 $04 Outlet structure - 17 cfs capacity LS $15,000 0 $0 0 $0 1 $15,0005 Riprap spillway protection CY $60 4 $240 8 $480 29 $1,740 1.5' thickness; 4:1 slope6 Concrete spillway weir CY $400 0.3 $120 0.4 $160 0.9 $3607 Maintenance access road (aggregate base course) CY $40 41 $1,640 56 $2,240 97 $3,880 basin length + 2 bottom accesses8 Upland seeding and mulching AC $2,000 0.09 $180 0.14 $280 0.28 $560 2*(top area-permanent pool area)9 Wetland vegetation AC $15,000 0.02 $300 0.04 $600 0.19 $2,85010 18" RCP LF $50 50 $2,500 50 $2,500 0 $011 24" RCP LF $55 0 $0 0 $0 50 $2,750


20 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsCWB 8/3/2009

Retention Pond (RP) with WQCV

Design Information

WQCV depth range 2-5 ftForebay depth (below permanent pool) 3 ftPermanent pool volume range (% of WQCV) 120%-200%Forebay volume (% of WQCV) 8%Basin length:width ratio 3Side slopes (H:V) 5Maintenance road width 10 ftMaintenance road slope 0.10 ft/ftMaintenance road thickness 1.0 ftWetland vegetation area (% of permanent pool) 35%

WQCV 2904 cf 7260 cf 29040 cfWQCV depth 2 ft 2 ft 3 ft100-yr peak flow 12 cfs 28 cfs 98 cfsWQ event peak flow 2.1 cfs 5.1 cfs 16.7 cfs used for calculating pipe size assuming 1% slopePermanent pool volume (% of WQCV) 160% 160% 120%Permanent pool volume 4646 cf 11616 cf 34848 cfForebay volume 232 cf 581 cf 2323 cfForebay area 77 sf 194 sf 774 sfArea at 1/2 WQCV depth 1452 sf 3630 sf 9680 sfWidth at 1/2 WQCV depth 22 ft 35 ft 57 ftLength at 1/2 WQCV depth 66 ft 104 ft 170 ftTop area 2432 sf 5121 sf 13313 sfPermanent pool area 672 sf 2339 sf 6497 sfAverage permanent pool depth 6.9 ft 5.0 ft 5.4 ftEmergency spillway width (assume 1' head) 4 ft 9 ft 33 ftMaintenance road length 106 ft 144 ft 230 ft


1 Excavation and backfill CY $5 280 $1,398 699 $3,496 1828 $9,142Permanent pool plus: 100% WQCV for 2 & 5 acre sites, 50% WQCV for 20 acre site

2 Concrete forebay CY $400 2 $800 4 $1,600 15 $6,000 qty based on area*2 for sides, ramps, etc.3 Outlet structure - 2.1 and 5.1 cfs capacity LS $10,000 1 $10,000 1 $10,000 0 $04 Outlet structure - 17 cfs capacity LS $15,000 0 $0 0 $0 1 $15,0005 Riprap spillway protection CY $60 4 $240 10 $600 36 $2,160 1.5' thickness6 Concrete spillway weir CY $400 0.3 $120 0.4 $160 0.9 $3607 Maintenance access road (aggregate base course) CY $40 39 $1,560 53 $2,120 85 $3,400 basin length + 2 bottom accesses8 Upland seeding and mulching AC $2,000 0.09 $180 0.13 $260 0.32 $640 2*(top area-permanent pool area)9 Wetland vegetation AC $15,000 0.01 $150 0.02 $300 0.06 $90010 Underdrain (incl. bedding and backfill) LF $30 66 $1,980 104 $3,131 170 $5,11211 18" RCP LF $50 50 $2,500 50 $2,500 0 $012 24" RCP LF $55 0 $0 0 $0 50 $2,750


20 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsRP 8/3/2009

Sand Filter Basin (SFB)

Design Information

a) Max WQCV depth 3 ftb) Length to width ratio (L/W) 2c) Depth of sand layer 18 in 1.5 ftd) Depth of gravel layer 8 in 0.67 fte) Total depth (a+c+d) 5.17 ft

g) WQCV 1815 cf 3630 cf 9075 cfh) Area 605 sf 1210 sf 3025 sfi) Width 17 ft 25 ft 39 ftj) Length 36 ft 48 ft 78 ft

k) # of runs of underdrain (20' spacing) 1 2 2l) Pipe diameter 18 in 24 in 30 in


1 Excavation and backfill CY $5 180 $900 310 $1,550 710 $3,550 e*(i+e)*(j+e)2 Sand CY $40 34 $1,360 67 $2,680 168 $6,720 h*c3 Gravel CY $40 15 $600 30 $1,200 75 $3,000 h*d4 4" perforated PVC pipe and fittings (incl. cleanouts) LF $20 36 $720 96 $1,920 156 $3,120 j*k5 Geotextile SY $4 203 $812 356 $1,424 816 $3,264 2*(i+e)*(j+e)6 Outlet structure - 6.3 and 12 cfs capacity LS $3,700 1 $3,700 1 $3,700 0 $0 Type C Inlet7 Outlet structure - 28 cfs capacity LS $4,300 0 $0 0 $0 1 $4,300 Type D Inlet8 Riprap outlet protection CY $60 0.9 $54 1.7 $102 2.6 $156 9*l2*1.259 18" RCP LF $50 50 $2,500 0 $0 0 $010 24" RCP LF $55 0 $0 50 $2,750 0 $011 30" RCP LF $75 0 $0 0 $0 50 $3,750

SUBTOTAL $10,646 $15,326 $27,860Mobilization and site prep 7% $745 $1,073 $1,950TOTAL COST $11,391 $16,399 $29,810

Add impermeable liner SY $6 101 $606 178 $1,068 408 $2,448Deduct geotextile SY $4 -101 -$404 -178 -$712 -408 -$1,632

ADD IMPERMEABLE LINER $202 $356 $816

5 Acre Site

Contributing Impervious Area1.0 ac 2.0 ac 5.0 ac

0.25 Acre Site 1 Acre Site

P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsSFB 8/3/2009

Porous Landscape Detention (PLD)

Design Information

a) Max WQCV depth 1 ftb) Length to width ratio (L/W) 2c) Depth of sand/peat layer 18 in 1.5 ftd) Depth of gravel layer 8 in 0.67 fte) Total depth (a+c+d) 3.17 ftf) Concrete perimeter wall area (e*0.5+1.5*0.5) 3.58 sf

Concrete rundown length 4.50 ftConcrete rundown width 3.00 ftConcrete rundown thickness 4.00 in 0.33 ft

g) WQCV 363 cf 1452 cf 7260 cfh) Area 363 sf 1452 sf 7260 sfi) Width 13 ft 27 ft 60 ftj) Length 28 ft 54 ft 121 ft

k) # of runs of underdrain (20' spacing) 1 2 3l) # of concrete rundowns (10' spacing) 3 6 13


1 Excavation and backfill CY $5 60 $300 210 $1,050 920 $4,600 e*(i+e)*(j+e)2 Concrete perimeter walls CY $400 11 $4,400 22 $8,800 49 $19,600 f*(2i+2j)3 Concrete rundowns CY $400 0.5 $200 1 $400 2.2 $8804 Sand/peat mixture CY $40 20 $800 81 $3,240 403 $16,120 h*c5 Gravel CY $40 9 $360 36 $1,440 179 $7,160 h*d6 4" perforated PVC pipe and fittings (incl. cleanouts) LF $20 28 $560 108 $2,160 363 $7,260 j*k7 Geotextile SY $4 112 $448 383 $1,532 1743 $6,972 2*(i+e)*(j+e)8 Outlet structure - 1.6 and 6.3 cfs capacity LS $3,700 1 $3,700 1 $3,700 0 $0 Type C inlet9 Outlet structure - 28 cfs capacity LS $4,300 0 $0 0 $0 1 $4,300 Type D inlet10 Landscaping SF $0.40 363 $145 1452 $581 7260 $2,90411 18" RCP LF $50 50 $2,500 50 $2,500 0 $012 30" RCP LF $75 0 $0 0 $0 50 $3,750

SUBTOTAL $13,413 $25,403 $73,546Mobilization and site prep 7% $939 $1,778 $5,148TOTAL COST $14,352 $27,181 $78,694

Add impermeable liner SY $6 56 $336 192 $1,152 871 $5,226Deduct geotextile SY $4 -56 -$224 -192 -$768 -871 -$3,484

ADD IMPERMEABLE LINER $112 $384 $1,742

Deduct concrete perimeter walls CY $400 -11 -$4,400 -22 -$8,800 -49 -$19,600Deduct concrete rundowns CY $400 -0.5 -$200 -1 -$400 -2.2 -$880Add riprap rundowns CY $60 2 $120 4 $240 8.8 $528 double width and thickness of concrete

DEDUCT FOR UNCONSTRAINED CONFIGURATION -$4,480 -$8,960 -$19,952Unconstrained Configuration Total Cost $9,872 $18,221 $58,742

5 Acre Site


0.25 Acre Site 1 Acre Site

P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsPLD 8/3/2009

Underground Vault with WQCV Detention

Design Information

Vault height 6.5 ftFreeboard 1.5 ftWQCV depth 5 ftVault length:width ratio 2Concrete wall thickness 0.67 ftDepth of cover 1 ftBedding thickness 1 ft

WQCV 544.8 cf 2178 cf 4356 cfWQCV Area 109 sf 436 sf 871 sfWidth 7.4 ft 14.8 ft 20.9 ftWQCV Length 14.8 ft 29.5 ft 41.7 ftTotal length 18.4 ft 33.2 ft 45.4 ftTotal vault area 136 sf 490 sf 948 sf

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total Notes1 Excavation and backfill CY $5 50 $248 178 $892 345 $1,7262 Structural concrete CY $800 18 $14,400 45 $36,000 76 $60,800 includes orifice plate, manhole covers, manhole steps, etc.3 Bedding material CY $40 8 $320 22 $880 41 $1,6404 18" RCP LF $50 50 $2,500 50 $2,500 0 $05 24" RCP LF $55 0 $0 0 $0 50 $2,750


2.0 Acre Site


0.25 Acre Site 1.0 Acre Site

P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsWQCV VAULT 8/3/2009

Underground Sand Filter Vault

Design Information

Vault height over sand filter 6.5 ftWQCV depth 3 ftSand filter length:width ratio 2Concrete wall thickness 0.67 ftSand layer thickness 1.5 ftGravel layer thickness 0.67 ftTotal vault height 8.67 ftUpstream weir wall height 3.17 ftDownstream weir wall height 5.17 ftDepth of cover 1 ftBedding thickness 1 ft

WQCV 454 cf 1815 cf 3630 cfWQCV Area 151 sf 605 sf 1210 sfWidth 8.7 ft 17.4 ft 24.6 ftSand filter length 17.4 ft 34.8 ft 49.2 ftTotal length 24.7 ft 42.1 ft 56.5 ftTotal vault area 215 sf 733 sf 1390 sf

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total Notes1 Excavation and backfill CY $5 96 $480 326 $1,630 619 $3,0952 Structural concrete CY $800 29 $23,200 70 $56,000 114 $91,200 includes orifice plate, manhole covers, manhole steps, etc.3 Sand CY $40 9 $360 34 $1,360 68 $2,7204 Gravel CY $40 4 $160 15 $600 30 $1,2005 Underdrain (4" Schedule 40 perforated PVC) LF $20 17 $348 35 $696 49 $9846 Bedding material CY $40 11 $440 32 $1,280 58 $2,3207 18" RCP LF $50 50 $2,500 50 $2,500 0 $08 24" RCP LF $55 0 $0 0 $0 50 $2,750


2.0 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsSFB VAULT 8/3/2009

Appendix D

Cost Spreadsheets and Figures for Porous Pavement BMPs

Modular Block Pavement (MBP)

Design Information

a Void area 40%b Design area ratio (impervious:pervious area) 2c Modular block height 3.15 in 0.26 ft 8 cmd Leveling course thickness 2 in 0.17 fte Base course thickness 8 in 0.67 ftf Underdrain layer thickness 6 in 0.5 ftg Perimeter wall cutoff depth 12 in 1 fth Perimeter wall thickness 6 in 0.5 fti Total wall height 31.15 in 2.60 ftj Slope 0.02 ft/ft

k Lmax between cells 20.00l Area of 4" pipe 12.57 in^2 0.087 ft^2

m Area of Single Paver Block 2.5 ft^2

Pavement area 0.083 ac 0.333 ac 0.667 acA Pavement area 3630 sf 14520 sf 29040 sfL Pavement length 20 ft 40 ft 40 ft

W Pavement width 181.5 ft 363 ft 726 ftn Number of cells 1 2 2o Length of each cell 20 20 20

sand=(A*d+c*A*a)/27geotextile = n*[W*(4c+4d+2e+2f+2o)]/9UnderDrain=Width* CellsConcrete Walls= (2*L+2*W)*h*i/27Base layer=(e*A+n*(f^2-l)*W)/27Impermeable barriers=(n-1)*(3*f+e)*W/9Excavation Calculations=Area*(c+d+e)/27+(5*5*5)*n/27+Item no. 94" PVC Pipe =5*n+(n-1)*20+50

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total1 Excavation and backfill CY $5 171 $857 637 $3,187 1261 $6,3072 Paver Blocks - includes leveling course and in-fill material SF $4 3630 $14,520 14520 $58,080 29040 $116,1603 Base course (AASHTO No. 3 coarse aggregate) CY $40 91 $3,629 363 $14,516 726 $29,0324 Geotextile SY $4 888 $3,553 3,553 $14,213 7,107 $28,4275 Underdrain (4" Schedule 40 perforated PVC) LF $12 182 $2,178 726 $8,712 1,452 $17,4246 Concrete perimeter walls CY $400 19 $7,749 39 $15,498 74 $29,4587 Impermeable flow barriers SY $6 0 $0 87 $524 175 $1,0498 4" PVC pipe LF $12 55 $660 80 $960 80 $9609 Utility vault (incl. riser pipes, orifice, etc.) EA $3,800 1 $3,800 2 $7,600 2 $7,600


Add impermeable liner SY $6 468 $2,806 1,871 $11,225 3,742 $22,449Deduct geotextile SY $4 -468 -$1,871 -1,871 -$7,483 -3,742 -$14,966

ADD IMPERMEABLE LINER $935 $3,742 $7,483

`

2.0 Acre Site

Contributing Impervious Area (ac)0.25 1.0 2.0


P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsMBP 8/3/2009

Cobblestone Block Pavement (CBP)

Design Information

a Void area 8%b Design area ratio (impervious:pervious area) 2c Cobblestone block height 3.15 in 0.262 ft 8 cmd Leveling course thickness 2 in 0.167 fte Base course thickness 7 in 0.583 ftf Sand layer thickness (including cushion layer) 7 in 0.583 ftg Underdrain layer thickness 6 in 0.5 fth Perimeter wall cutoff depth 12 in 1 fti Perimeter wall thickness 6 in 0.5 ftj Total wall height 37.15 in 3.10 ft

k Slope 0.02 ft/ftl Lmax between cells 20.00

m Area of 4" pipe 12.57 in^2 0.087 ft^2p Length of geotextile under ASTM C-33 Sand 24 in 2



in-fill & leveling=(area*e+c*area*a)/27Base layer=[(e*A+n*(f*f-m)*W)]/27Sand=(A*f)/27geotextile = n*[W*(7c+7d+5e+3f+2g+3o+p)]/9UnderDrain=W*n+5*n+(n-1)*20+50Concrete Walls= (2*L+2*W)*i*j/27Impermeable barriers=(n-1)*(3*g+f+e+f)*W/9Excavation Calculations=Area*(c+d+e+f)/27+(5*5*5)*n/27+Item no. 10

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total1 Excavation and backfill CY $5 242 $1,211 914 $4,568 1813 $9,0672 Paver Block - includes leveling course and in-fill material SF $5.50 3,630 $19,965 14,520 $79,860 29,040 $159,7203 Base course (AASHTO No. 67 coarse aggregate) CY $40 80 $3,181 318 $12,723 636 $25,4464 Sand (ASTM C-33) CY $40 78 $3,137 314 $12,548 627 $25,0965 Geotextile SY $4 1,425 $5,701 5,701 $22,803 11,402 $45,6066 Underdrain (4" Schedule 40 perforated PVC) LF $12 182 $2,178 726 $8,712 1,452 $17,4247 Concrete perimeter walls CY $400 23 $9,242 46 $18,483 88 $35,1328 Impermeable flow barriers SY $6 0 $0 94 $565 188 $1,1299 4" PVC pipe LF $12 55 $660 80 $960 80 $96010 Utility vault (incl. riser pipes, orifice, etc.) EA $3,800 1 $3,800 2 $7,600 2 $7,600




2.0 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsCBP 8/3/2009

Reinforced Grass Pavement (RGP)

Design Information

a Ring Void Percentage 92.00%b Design area ratio (impervious:pervious area) 2c Leveling course thickness (sand) 1 in 0.083 ftd Base course thickness (sandy gravel) 10 in 0.833 fte Ring Height 1 in 0.083 ft

Pavement area 0.083 ac 0.333 ac 0.667 acPavement area 3630 sf 14520 sf 29040 sfPavement length 20 ft 40 ft 40 ftPavement width 181.5 ft 363 ft 726 ft

sand=((area*c)+(area*e*a))/27Base Course=(area*d)/27geotextile=((Length+2(c+d))*Width)/9Excavation Calculation=Area*(c+d)/27

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total1 Excavation and backfill CY $5 123 $616 493 $2,465 986 $4,9302 Sand (ASTM C-33) CY $40 22 $860 86 $3,442 172 $6,8844 Base course (60% AASHTO No. 67 Aggregate, 40% ASTM C-33 Sand) CY $40 112 $4,481 448 $17,926 896 $35,8523 Geotextile SY $4 440 $1,761 1,687 $6,749 3,375 $13,4985 GrassPave SF $4 3630 $14,520 14520 $58,080 29040 $116,1606 Sod SF $0.60 3630 $2,178 14520 $8,712 29040 $17,424




2.0 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsRGP 8/3/2009

Porous Concrete Pavement (PCP)

Design Information

a Design area ratio (impervious:pervious area) 2b Base course thickness 8 in 0.666667 ftc Sand layer thickness (including cushion) 7 in 0.583333 ftd Underdrain layer thickness 6 in 0.5 fte Slope 0.02 ft/ftf Lmax between cells 20.00 ftg Area of 4" pipe 12.57 in^2 0.087266 ft^2h Length of geotextile under ASTM C-33 Sand 24.00 in 2 fti Concrete thickness 5.00 in 0.416667 ft



Base course=(A*b+(d^2-g)*n*W)/27Sand=A*c/27geotextile =n*W*(4*b+2*c+2*o)/9UnderDrain=W*n+5*n+(n-1)*20+50Impermeable flow barrier=(n*W*(h+2*d+b+c))/9Excavation Calculations=Area*(i+b+c)/27+(5*5*5)*n/27

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total1 Excavation and backfill CY $5 229 $1,144 906 $4,528 1802 $9,0092 Porous concrete CY $350 56 $19,606 224 $78,426 448 $156,852 unit cost 130% std concrete paving3 Base course (AASHTO No. 3 coarse aggregate) CY $40 91 $3,629 363 $14,516 726 $29,0324 Sand (ASTM C-33) CY $40 78 $3,137 314 $12,548 627 $25,0965 Geotextile SY $4 884 $3,536 3,536 $14,144 7,072 $28,2876 Underdrain (4" Schedule 40 perforated PVC) LF $12 182 $2,178 726 $8,712 1,452 $17,4247 Impermeable flow barrier SY $6 86 $514 343 $2,057 686 $4,1148 4" PVC pipe LF $12 55 $660 80 $960 80 $9609 Utility vault (incl. riser pipes, orifice, etc.) EA $3,800 1 $3,800 2 $7,600 2 $7,600




2.0 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsPCP 8/3/2009

Porous Gravel Pavement (PGP)

Design Information

a Design area ratio (impervious:pervious area) 2b Base course thickness 12 in 1 ftc Sand layer thickness (including cushion) 7 in 0.583333 ftd Underdrain layer thickness 6 in 0.5 fte Slope 0.02 ft/ftf Lmax between cells 20.00 ftg Area of 4" pipe 12.57 in^2 0.087266 ft^2h Length of geotextile under ASTM C-33 Sand 24.00 in 2 ft



Base course=(A*b+(d^2-g)*n*W)/27Sand=A*c/27geotextile =n*W*(4*b+2*c+2*o)/9UnderDrain=W*n+5*n+(n-1)*20+50Impermeable flow barrier=(n*W*(h+2*d+b+c))/9Excavation Calculations=Area*(b+c)/27+(5*5*5)*n/27

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total1 Excavation and backfill CY $5 218 $1,088 861 $4,304 1712 $8,5612 Base course (AASHTO No. 3 coarse aggregate) CY $40 136 $5,422 542 $21,686 1084 $43,3723 Sand (ASTM C-33) CY $40 78 $3,137 314 $12,548 627 $25,0964 Geotextile SY $4 911 $3,643 3,643 $14,574 7,287 $29,1485 Underdrain (4" Schedule 40 perforated PVC) LF $12 182 $2,178 726 $8,712 1,452 $17,4246 Impermeable flow barrier SY $6 92 $555 370 $2,218 739 $4,4377 4" PVC pipe LF $12 55 $660 80 $960 80 $9608 Utility vault (incl. riser pipes, orifice, etc.) EA $3,800 1 $3,800 2 $7,600 2 $7,600



ADD IMPERMEABLE LINER $1,402 $5,606 $11,213

2.0 Acre Site0.25 Acre Site 1.0 Acre Site


P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsPGP 8/3/2009

Appendix E

Summary of Types, Sizing, and Cost Information for Proprietary BMPs

Type of Device Manufacturer InformationHydrodynamic Separators

Model Number Volume of Model

(cf)% Of WQCV (w/ Sediment Sto.

CostInstalled Cost

Model Number Volume of Model% Of WQCV (w/ Sediment Sto.

Cost Installed Cost Model Number Volume of Model% Of WQCV (w/ Sediment Sto.

Cost Installed Cost

VortechsCONTECH Stormwater Solutions

Hydrodynamic Separator with swirl chamber, baffle wall.

V2000 120 22.0 $16,500 $24,750 V 5000 273 12.5 $24,600 $36,900.0 V 11000 480 11.0 $41,000 $61,500

Stormceptor STC Imbrium

Hydrodynamic Separator, different types including submerged, in‐line, series, and inlet version. Was informed that prices were very close to the OSR

model (see Oil/Grease Separators)

STC 450i 60.15 11.0 $8,000 $12,000 STC 900 120 5.5 $11,000 $16,500.0 STC 2400 321 7.4 $21,000 $31,500

Contech CDSCONTECH Stormwater Solutions

Hydrodynamic Separator CDS 2015 92 16.8 $7,500 $11,250 CDS 2020 103 4.7 $13,000 $19,500 CDS 3020 167 3.8 $23,500 $35,250

ecoStorm WaterTectonics Hydrodynamic Separator, price includes shipping Model 1 141 26.0 $16,700 $25,050 Model 2 251 11.5 $32,400 $48,600 Model 3 393 9.0 $51,100 $76,650

Average: $18,263 Average: $30,375 Average: $51,225 Oil/Grease/Sediment

Separator Model Number Cost

Installed Cost

Model Number Cost Installed Cost Model Number Cost Installed Cost

Stormceptor OSR Imbrium Oil and Grease Separator, Fiberglass Construction

AvailableOSR 065 $7,400 $11,100 OSR 140 $10,700 $16,050 OSR 250 $18,600 $27,900

SandOil OldCastle Precast Sand/Oil Interceptor

ecoLine B WaterTectonics Oil and Grease Separator, Prices include shipping160 gpm Model‐

Dual Tank$12,900 $19,350

630 gpm Model‐Dual Tank

$30,400 $45,600 2x 630 gpm Model‐

Dual Tank$60,800 $91,200

Average: $15,225 Average: $30,825 Average: $59,550

Media Filtration Model Number Filter Area (sq. ft.) System gpm/sf CostInstalled Cost

Model Number Filter Area System gpm/sf Cost Installed Cost Model Number Filter Area System gpm/sf Cost Installed Cost

ecoStorm Plus WaterTectonicsPorous Concrete Media Filter w/Hydrodynamic

Separator and sediment sump with outlet preventing floatable oils from escaping

A single ecoStorm Plus with an

upstream CB drop structure

78.5 2 $34,000 $51,000 2 ecoStorm Plus

units with a Model 2 ecoStorm upstream

157.1 3 $96,000 $144,000 3 ecoStorm Plus

units with a Model 3 ecoStorm upstream

235.6 4 $146,500 $219,750

FilterraFilterra Bioretention

Systems BioFilter with a form of plant life in boxes of

different size.

Filterra 4x8 plus 1 Type R Inlet @

$400032 4 $9,700 $18,550

2 Filterra 6x10s at $17,100 ea plus 2 Type R inlets @$4000 ea

120 4 $34,200 $59,300

3 Filterra 6x10s at $17,100 ea plus 3 Type R inlets @

$4000 ea

180 5 $51,300 $88,950

StormFilterCONTECH

Construction Products

Media Filter involving different cartridges 9 Cartridge Vault 2 $25,000 $37,500 33 Cartdrige Vault 2 $52,500 $78,750 63 Cartridge Vault 2 $105,000 $157,500

Oil/Water Filter OldCastle PrecastMedia Filter includes sudge weir and Coalescing

Media160 OW 640 OW 2*480 OW at


Inlet Inserts # of Inlets System gpm/sf Unit CostTotal

Installed Cost

# of Inlets System gpm/sf Unit CostTotal Installed

Cost# of Inlets System gps/sf Unit Cost

Total Installed Cost

Hydroscreen Hydroscreen, LLCInlet Filter for fitting on curbs, pricing is based

$/sq. ft1 5.4 $3,750 $5,625 2 9.88 $7,500 $11,250 4 9.43 $15,000 $22,500

Ultra Urban Filter with Smart Sponge

AbTech Industries

Model Used is 13"x14"x13", Pricing for Filter + Collar. Collar price depending on material used,

which changes with each project: Max add $300 to Filter Cost

4 80 $700.00 $1,050 8 80 1100 $1,650 16 80 1900 $2,850

FlexStormFleXstorm Inlet

Filters

Inlet Filter that fits most gutters, differing prices for different size gutters. Filters generally hold 2

to 3 cubic feet of waste, $110 avg cost4 200 $110 $165 8 200 220 $330 16 200 440 $660


0.25 acre 1 acre 2 acre

Appendix F

Cost Spreadsheets and Figures for Channel BMPs

Constructed Wetlands Channel (CWC)

Design Information

2-yr peak flow 4.1 cfs 10 cfs 32 cfs100-yr peak flow 12 cfs 28 cfs 98 cfsBottom width 8 ft 8 ft 8 ftSide slopes 4 H:V 4 H:V 4 H:V100-yr depth (n=0.080) 1.5 ft 2.3 ft 4.0 ftChannel depth 2.5 ft 3.3 ft 5.0 ftChannel area 45 sf 70 sf 140 sfHeight of riprap protection above channel invert 2 ft 2 ft 2 ftChannel length 100 ft 100 ft 100 ft

UNIT COSTS PER 100 LINEAR FEET OF CHANNEL

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total Notes1 Excavation and backfill CY $5 167 $835 259 $1,295 519 $2,5952 Riprap bank protection (9" Type VL) CY $60 56 $3,360 56 $3,360 56 $3,3603 Wetland vegetation AC $15,000 0.02 $300 0.02 $300 0.02 $300 channel bottom4 Upland seeding and mulching AC $2,000 0.09 $180 0.12 $240 0.18 $360 channel banks plus equal width at top of bank

SUBTOTAL $4,675 $5,195 $6,615Mobilization and site prep 7% $327 $364 $463TOTAL COST / 100 LF $5,002 $5,559 $7,078

20 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsCWC 8/3/2009

Appendix G

Cost Spreadsheets for EURV BMPs

Extended Detention Basin (EDB) with EURV

Design Information

EURV depth range 3-5 ftForebay depth 2 ftForebay volume (% of WQCV) 4%Basin length:width ratio 3Side slopes (H:V) 5Maintenance road width 10 ftMaintenance road slope 0.10 ft/ftMaintenance road thickness 1.0 ft

WQCV (incl. sediment storage) 4356 cf 10890 cf 43560 cfEURV 8818 cf 22045 cf 88181 cfEURV depth 3 ft 3 ft 5 ft100-yr peak flow 12 cfs 28 cfs 98 cfsMax allowable release rate 2.0 cfs 5.0 cfs 20 cfs used for calculating pipe size assuming 1% slopeForebay volume 174 cf 436 cf 1742 cfForebay area 87 sf 218 sf 871 sfArea at 1/2 EURV depth 2939 sf 7348 sf 17636 sfWidth at 1/2 EURV depth 31 ft 49 ft 77 ftLength at 1/2 EURV depth 94 ft 148 ft 230 ftTop area 5042 sf 10543 sf 25928 sfBottom area 1286 sf 4604 sf 10594 sfEmergency spillway width (assume 1' head) 4 ft 9 ft 33 ftMaintenance road length 154 ft 208 ft 330 ftTrickle channel width 2 ft 2 ft 4 ftTrickle channel length 63 ft 99 ft 153 ft

Item No. Item Unit Unit Price Quantity Total Quantity Total Quantity Total Notes1 Excavation and backfill CY $5 327 $1,633 816 $4,082 1633 $8,165 100% EURV for 2 & 5 acre sites, 50% EURV for 20 acre site2 Concrete forebay CY $400 2 $800 5 $2,000 17 $6,800 qty based on area*2 for sides, ramps, etc.3 Outlet structure - 2.0 and 5.0 cfs capacity LS $10,000 1 $10,000 1 $10,000 0 $04 Outlet structure - 20 cfs capacity LS $15,000 0 $0 0 $0 1 $15,0005 Riprap spillway protection CY $60 6 $360 15 $900 51 $3,060 1.5' thickness; 4:1 slope6 Concrete spillway weir CY $400 0.3 $120 0.4 $160 0.9 $3607 Maintenance access road (aggregate base course) CY $40 57 $2,280 77 $3,080 122 $4,880 basin length + 2 bottom accesses8 Upland seeding and mulching AC $2,000 0.14 $280 0.30 $600 0.72 $1,440 120% of top area9 18" RCP LF $50 50 $2,500 50 $2,500 0 $0

10 24" RCP LF $55 0 $0 0 $0 50 $2,75011 Concrete trickle channel CY $400 5 $2,000 7 $2,800 17 $6,800 2/3 basin length, 6" thick, 4" deep


20 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsEDB_EURV 8/3/2009

Constructed Wetlands Basin (CWB) with EURV

Design Information

EURV depth range 3-5 ftForebay depth (below permanent pool) 3 ftPermanent pool volume (% of WQCV) 75%Forebay volume (% of WQCV) 8%Basin length:width ratio 3Side slopes (H:V) 5Maintenance road width 10 ftMaintenance road slope 0.10 ft/ftMaintenance road thickness 1.0 ftWetland vegetation area (% of permanent pool) 60%

WQCV 3267 cf 8168 cf 32670 cfEURV 8818 cf 22045 cf 88181 cfEURV depth 3 ft 4 ft 5 ft100-yr peak flow 12 cfs 28 cfs 98 cfsMax allowable release rate 2.0 cfs 5.0 cfs 20 cfs used for calculating pipe size assuming 1% slopePermanent pool volume 2450 cf 6126 cf 24503 cfForebay volume 261 cf 653 cf 2614 cfForebay area 87 sf 218 sf 871 sfArea at 1/2 EURV depth 2939 sf 5511 sf 17636 sfWidth at 1/2 EURV depth 31 ft 43 ft 77 ftLength at 1/2 EURV depth 94 ft 129 ft 230 ftTop area 5042 sf 9340 sf 25928 sfPermanent pool area 1286 sf 2482 sf 10594 sfAverage permanent pool depth 1.9 ft 2.5 ft 2.3 ftEmergency spillway width (assume 1' head) 4 ft 9 ft 33 ftMaintenance road length 154 ft 189 ft 290 ft


1 Excavation and backfill CY $5 417 $2,087 1043 $5,217 2540 $12,702Permanent pool plus: 100% EURV for 2 & 5 acre sites, 50% EURV for 20 acre site

2 Concrete forebay CY $400 4 $1,600 9 $3,600 33 $13,200 qty based on area*2 for sides, ramps, etc.3 Outlet structure - 2.0 and 5.0 cfs capacity LS $10,000 1 $10,000 1 $10,000 0 $04 Outlet structure - 20 cfs capacity LS $15,000 0 $0 0 $0 1 $15,0005 Riprap spillway protection CY $60 4 $240 10 $600 36 $2,160 1.5' thickness; 4:1 slope6 Concrete spillway weir CY $400 0.3 $120 0.4 $160 0.9 $3607 Maintenance access road (aggregate base course) CY $40 57 $2,280 70 $2,800 107 $4,280 basin length + 2 bottom accesses8 Upland seeding and mulching AC $2,000 0.18 $360 0.32 $640 0.71 $1,420 2*(top area-permanent pool area)9 Wetland vegetation AC $15,000 0.02 $300 0.04 $600 0.15 $2,25010 18" RCP LF $50 50 $2,500 50 $2,500 0 $011 24" RCP LF $55 0 $0 0 $0 50 $2,750


20 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsCWB_EURV 8/3/2009

Retention Pond (RP) with EURV

Design Information

EURV depth range 3-6 ftForebay depth (below permanent pool) 3 ftPermanent pool volume range (% of WQCV) 120%-200%Forebay volume (% of WQCV) 8%Basin length:width ratio 3Side slopes (H:V) 5Maintenance road width 10 ftMaintenance road slope 0.10 ft/ftMaintenance road thickness 1.0 ftWetland vegetation area (% of permanent pool) 35%

WQCV 2904 cf 7260 cf 29040 cfEURV 8818 cf 22045 cf 88181 cfEURV depth 3 ft 4 ft 6 ft100-yr peak flow 12 cfs 28 cfs 98 cfsMax allowable release rate 2.0 cfs 5.0 cfs 20 cfs used for calculating pipe size assuming 1% slopePermanent pool volume (% of WQCV) 160% 160% 120%Permanent pool volume 4646 cf 11616 cf 34848 cfForebay volume 232 cf 581 cf 2323 cfForebay area 77 sf 194 sf 774 sfArea at 1/2 EURV depth 2939 sf 5511 sf 14697 sfWidth at 1/2 EURV depth 31 ft 43 ft 70 ftLength at 1/2 EURV depth 94 ft 129 ft 210 ftTop area 5042 sf 9340 sf 23996 sfPermanent pool area 1286 sf 2482 sf 7198 sfAverage permanent pool depth 3.6 ft 4.7 ft 4.8 ftEmergency spillway width (assume 1' head) 4 ft 9 ft 33 ftMaintenance road length 154 ft 209 ft 330 ft


1 Excavation and backfill CY $5 499 $2,493 1247 $6,234 2924 $14,618Permanent pool plus: 100% EURV for 2 & 5 acre sites, 50% EURV for 20 acre site

2 Concrete forebay CY $400 2 $800 4 $1,600 15 $6,000 qty based on area*2 for sides, ramps, etc.3 Outlet structure - 2.0 and 5.0 cfs capacity LS $10,000 1 $10,000 1 $10,000 0 $04 Outlet structure - 20 cfs capacity LS $15,000 0 $0 0 $0 1 $15,0005 Riprap spillway protection CY $60 7 $420 17 $1,020 58 $3,480 1.5' thickness6 Concrete spillway weir CY $400 0.3 $120 0.4 $160 0.9 $3607 Maintenance access road (aggregate base course) CY $40 57 $2,280 77 $3,080 122 $4,880 basin length + 2 bottom accesses8 Upland seeding and mulching AC $2,000 0.18 $360 0.32 $640 0.78 $1,560 2*(top area-permanent pool area)9 Wetland vegetation AC $15,000 0.02 $300 0.02 $300 0.06 $90010 Underdrain (incl. bedding and backfill) LF $30 94 $2,817 129 $3,858 210 $6,29911 18" RCP LF $50 50 $2,500 50 $2,500 0 $012 24" RCP LF $55 0 $0 0 $0 50 $2,750


20 Acre Site



P:\07-030 UDFCD Misc Jobs\06 BMP Costs\Excel\Costs_rev.xlsRP_EURV 8/3/2009

Appendix H

Resource Contact Information

PERMANENT BMP COST ESTIMATES ‐ RESOURCES

Manufacturer Products Contact Name Contact Information

CONTECH Stormwater Solutions

Vortechs, Contech CDS, StormFilter

Duane Herring herringd@contech‐cpi.com

Imbrium/Rinker Materials

Stormceptor STC, Stormceptor OSR

Brian Schram [email protected]

WaterTectonicsEcoStorm, EcoLine B, EcoStorm

PlusTJ Mothersbaugh [email protected]

Filterra Bioretention Systems

Filterra Media Filtration Will Harris [email protected]

Hydroscreen, LLC Hydroscreen Inlet Filter Bob Weir 303‐333‐6071

AbTech Industries Urban Filter with Smart Sponge Chris Bradley 480‐874‐4000

FlexStorm Inlet Filters FleXstorm Inlet Filter Jamie Ringenbach [email protected]

StevensCorp grasspave2 Jay Stevens [email protected]

Pavestone Grasstone II, Uni Eco‐Stone John Rowe303‐287‐3700

[email protected]

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